


Inexplicable

by emmagrant01



Category: Sherlock (TV), Sherlock Holmes & Related Fandoms
Genre: Angst, Bodyswap, Consensual Infidelity, F/M, Infidelity, M/M, Magical Artifacts, Sherlock Series 3 Spoilers, Spoilers: The Sign of Three, crossover of sorts
Language: English
Status: Completed
Published: 2014-02-05
Updated: 2014-03-12
Packaged: 2018-01-11 06:59:51
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 34,664
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/1170065
Author URL: https://archiveofourown.org/users/emmagrant01/pseuds/emmagrant01
Summary: <blockquote class="userstuff">
              <p>So what was in that matchbox, anyway? John and Sherlock find out, the hard way.</p>
            </blockquote>





	1. One

**Author's Note:**

  * Translation into Polski available: [Niewytłumaczalne](https://archiveofourown.org/works/1348414) by [KittensAndRage](https://archiveofourown.org/users/KittensAndRage/pseuds/KittensAndRage)
  * Inspired by [Method Act](https://archiveofourown.org/works/1139576) by [splix](https://archiveofourown.org/users/splix/pseuds/splix). 



> • Partially inspired by Splix's glorious new WIP, [Method Act](http://archiveofourown.org/works/1139576), in which Benedict Cumberbatch and Sherlock Holmes switch places in their respective universes, and the results are amazing. It got me thinking that I've never written a body swap fic before. So here goes!  
> • Also written for Let's Write Sherlock's [Missing Scene Challenge](http://letswritesherlock.tumblr.com/post/74672938345/sorry-for-the-wait-everyone-but-here-is-our-new).  
> • Dialogue from The Sign of Three taken from Ariane Devere's [transcript](http://arianedevere.livejournal.com/65379.html).  
> • Huge thanks as always to Drinkingcocoa, whose comments and cheerleading are invaluable! I really needed both this time around.

John settled at the table with a cup of tea. As Saturday mornings with Sherlock went, it had been a quiet one, but he didn't mind. All the better to catch up on the blog, write up some new cases. He glanced over at Sherlock, who was staring at a small object held between his fingers. 

"What is that?"

Sherlock looked up. "A French decathlete found completely out of his mind, surrounded by one thousand, eight hundred and twelve matchboxes – all empty except this one." 

"And what’s in that one?"

"The inexplicable." 

He slid the cover of the matchbox open and it emitted an otherworldy yellowish glow. A genuine smile spread across Sherlock's face, the sort that usually accompanied the discovery of human body parts or the revelation that a serial killer was on the loose. John stood and crossed the room for a closer look, but the box appeared to be empty except for the astonishingly bright light. 

"That's quite a trick. How does it work?"

"No idea." Sherlock tilted the box to get a better view inside.

"Fiber optics, has to be."

"I thought so at first, but I haven't been able to detect anything other than paper in the interior. Whoever made this did a fantastic job of concealing the power source as well." 

They both stared at the light for a long moment.

"So you said the man – the decathlete – went mad."

"Yes." 

John waited for him to elaborate, but Sherlock continued to stare at the light instead, apparently transfixed. "Sherlock?" John put his hand on Sherlock's shoulder. "Maybe we shouldn't—"

There was a strange sensation right behind his navel, something that was immediately alarming and unidentifiable, and then darkness pressed in all around.

*****

John groaned, disoriented. Awareness began to seep back in: He was sitting in a chair and his head was pounding. Must've fallen, hit his head on something, and Sherlock had helped him into this chair. It wasn't his chair: the cushion felt all wrong and the light coming in through the window was at the wrong angle; he could tell even through his closed eyelids. Sherlock's chair then. Which meant Sherlock had seen him pass out, had probably lugged him off the floor and into this chair. 

John opened his eyes and winced at the brightness of the daylight. "Oh, hell. Sherlock?" 

There was no answer. Perhaps he'd gone down to get help? The pain in John's head flared again, and he lifted his hand, pressed his fingers against the spot where he assumed he'd hit it on the floor. No way to know which direction he'd fallen; backwards seemed unlikely, given the position he'd been in. The fact that he was leaning forward at the time seemed to indicate that—

 _Hair_. He touched his head again, combed his fingers into hair that was not his, that was much longer and finer, that tangled around his fingertips. He gave it a tug, and yes: it was definitely attached to his scalp. He frowned: he must've hit his head harder than he'd thought. 

There was a sharp intake of breath from his left, and he turned his head to see a person on the floor pushing himself up to sitting. John's eyes refused to focus for a moment, but even through the fuzz, it didn't seem to be Sherlock. His attacker, perhaps? Multiple escape strategies flitted through his mind and he clenched the arms of the chair, prepared to stand. 

His eyes suddenly focused, and he nearly shouted at the sight before him. That was… _him_ , sitting on the floor. He closed his eyes and opened them again, but the scene didn't change: He, John, was sitting in this chair and looking at _himself_ – who was staring back at him with a look of horror on his face.

"What's going on?" The voice that came out of him, that rumbled in his ears, was distinctly not his own. 

"I don't know," the John on the floor said, and then appeared to have the same revelation about his own voice. He looked down at his hands and his body and went very, very pale.

"Sherlock?" John called, and the John on the floor looked up at him, forehead creased.

"John?"

"Oh, no. No no no." John shook his head and stood, suddenly filled with manic energy. "This is not possible, it's… whoa." Vertigo. The room looked completely different than it had before, shifted, as if he were… taller. Much taller. He reached out to put a hand on the back of the chair, and had to try twice, because it was several inches lower than he'd expected. He looked down.

That was not his hand, nor was it his arm, or his clothing. With a desperately sinking feeling, he turned to look at his reflection in the mirror above the fireplace.

Sherlock's face stared right back at him. 

"Bloody hell." The words looked incredibly bizarre coming out of Sherlock's mouth, but yes, there was no denying that he was, somehow, against all explanation or logic… _Sherlock_. Behind him, Sherlock – apparently – clambered to his feet and stared at his own reflection, slack-jawed. John's eyes met his in the mirror. "What do we do?"

"I have no idea." Sherlock crossed to stand next to him and went up on his toes. "This is completely unexpected."

"Unexpected? Is that the best you can do? Christ, Sherlock, look at us! What the hell is going on?"

"There is no logical explanation, but yet, here we are." Sherlock – and God, it was hard to call him that when all John could see was his own face – squinted at himself in the mirror. "I had no idea you were so short."

John gave him an incredulous look. "We're standing here in each other's bodies, and _that's_ what you're thinking about?"

Sherlock ran his fingers through John's short hair, ruffling it a bit. "Or that you look so old." He made a face in the mirror. 

John made a sound of frustration and turned away. He felt incredibly wound up, so much so that he was compelled to move, to pace, to bounce on the balls of his feet. "What the hell was in that matchbox?"

Sherlock turned and scanned the floor around them. "Yes, that's as good a starting point as any. Let's see, where might it have— Aha, here it is." Sherlock reached under the sofa table and came up with the matchbox in his hand.

"Right, of course. We might be able to reverse the… whatever it was. We should recreate the exact moment." 

"Yes, I think so. Precisely as we were."

"But which way? Bodies, or…?" John gestured between them. 

"Or what?"

"I don't know. Souls?"

Sherlock's expression was sheer derision. "There's no such thing as a soul."

"Then how else would you explain the fact that we're _in each other's bodies_?" John took a step back and put his hands on his head, desperately trying to keep himself from flailing them. "Why am I the only one freaking out about this? How can you be so calm?" 

Sherlock watched him with fascination. "God, I had no idea I looked that ridiculous when I'm being unreasonable."

" _I'm_ being unreasonable? Me?"

There was a distinct flash of irritation on Sherlock's face. "God, will you—just sit. Let's give it a go."

"Fine." John flopped into Sherlock's chair. "You opened the matchbox and then we both stared at it, and I touched your shoulder. That's when it happened, right?"

Sherlock moved to stand behind him. "Yes." 

"Let's try it." John held up the matchbox and slid the cover off, but nothing happened. There was no mysterious glow – it seemed to be an ordinary matchbox again. John tilted it, looked inside, and frowned. It was quite ordinary indeed. The strike strip on the side of the box had never been used and the print on the label was of good quality. The label design seemed intentionally old-fashioned, with a stylized W prominently featured in the logo. He was reminded of the sort of matches his grandfather used to buy to light his pipe, and — he shook his head. _Focus_. Sherlock swore softly behind him, and John shook his head, forced himself to stop thinking. "Come on, stare at it anyway. Repeat everything just as we did it before." 

It didn't work, and so they reversed positions, tried it again. Still nothing. 

"Let's keep trying," John said, turning to look around the room. "You were – I mean, I was at the table to start with, and maybe it makes a difference. Maybe we should say the same words we said, exactly, reproduce the conversation." 

"Exactly?" A look of panic began to spread over Sherlock's face. "I can't remember what I said." 

"It was five minutes ago. How can you not remember?" John remembered every word of it, even the cadence; it was all right there in his head. If he could recall it in that sort of detail, Sherlock ought to be able to do as well.

Sherlock looked back at him blankly.

"Fuck," John said, and turned toward the fireplace. "All right, fine. So use your mind palace, see if you've got anything like this in there."

"I don't…" Sherlock shook his head, eyes wide. "It's not there." 

"What do you mean, it's not there? How could it not be there?"

"It's my… whatever, _me_ , but it's your brain. Your neural pathways, your structures." He closed his eyes and frowned, concentrating. "All of my memories are intact, but they're harder to access. I don't even know where to begin to look." He pressed his fingertips against his temples for several seconds, and then dropped his hands in defeat. "Oh, God – is this what it's like to be stupid?"

John rounded on him. "I am not stupid. And I'm having trouble in your brain as well. God, how do you get anything done when you're so easily distracted?"

"I'm not easily distracted; you just don't know how to process information quickly enough!" He whirled and leveled a kick at John's chair. "Fuck!"

"Oh, for fuck's sake, will you calm down?"

"I don't know how! I can't think straight with all this… why are you so angry?"

"I'm not angry!"

"No, I mean—" He gestured at himself, and John's jaw clenched. Of course. Sherlock was feeling the fight-or-flight response of John's body, and it was probably overwhelming.

"Oh, God, why is this happening?" John took a deep breath. "Look, just… try to control it, and then let it go. Take a deep breath. Go splash water on your face or something. Give it a moment. I don't know how else to explain it." 

Sherlock made a sound of frustration, but turned toward the bathroom.

John sat on the sofa and exhaled. This was a nightmare. Perhaps a literal nightmare, and if so, he was going to be very happy in the morning. It made no sense that he was sitting here in Sherlock's body, that a fucking matchbox had done this. He didn't believe in anything remotely supernatural, had never done. 

Perhaps it would wear off. Maybe after a certain amount of time, they'd switch back. Or perhaps it was like _Freaky Friday_ and they had to learn an important lesson first. Oh, God – did they have to learn to appreciate each other's unique perspective on life or something inane like that?

The toilet flushed in the bathroom and the tap ran, and a whole fresh level of hell occurred to John. Living in each other's bodies meant they would get to know them very intimately. John groaned: there were things he didn't even want Mary to know, let alone his best friend. 

Sherlock reappeared, looking a bit sheepish. He'd removed John's cardigan and had unfastened the top few buttons on his shirt, and he'd done something weird with John's hair so that it stuck up in odd places. He looked like a lunatic version of John. He settled in John's chair with a strange expression on his face.

John sighed. "What?"

Sherlock opened his mouth, hesitated a moment, and then looked up at him. "Your penis is larger than I expected."

John blinked at him for a moment, shocked, and then tried valiantly to keep a straight face. "My… what?"

"At least 20% larger." Sherlock frowned, and John couldn't help himself: he laughed. It was probably a side-effect of the tension, or the strangely tenuous hold he had on his emotions in this body, but it bubbled out, bringing tears to his eyes, and he nearly slid off the sofa. 

He wiped at his eyes, still breathless from laughter. "So you're saying you've actually spent time thinking about the size of my penis?"

"I… No!" 

" _Expectation_ implies you have done."

"No, I meant… anticipated." At John's snort of laughter, he rolled his eyes and tried again. "Oh, God – _would have_ anticipated, given your height and build." His cheeks flushed pink, and he pressed his hands against them. "Why is this embarrassing me? I don't get embarrassed about this sort of thing."

"But I do," John said, still grinning. "Under normal circumstances, I'd find this conversation excruciatingly embarrassing." The fact that he didn't seem to mind it now was rather freeing.

"Fair warning, then. You're going to be a bit disappointed when it's your turn to take a piss." 

John nearly burst out laughing all over again. "How disappointed will I be?"

Sherlock scowled. "Well, not that disappointed. My penis is proportional to my body, at least."

"And mine isn't?" 

"Not in my experience."

"And you've got a lot of experience with cocks, have you?" John bit his lip to stop himself from grinning.

"Yes," Sherlock replied, and John could spot the precise moment he finally caught on. "Oh, God, no, not like that. I meant with corpses."

John raised his eyebrows. "Kinky."

"Ugh, fuck off." Sherlock made a very Sherlock-like expression of disgust, and it looked utterly incongruous on John's face. He shook his head and sank back into John's chair, expression turning serious once again. "I don't know what to do, John. I don't know how to fix this."

John sighed as the reality of the situation crashed down on him once again. "Neither do I. If we're going to be stuck like this for a while, comparing penises may be the least of our difficulties."

Sherlock closed his eyes. "I don't think I could bear to be you for the rest of my life. I can't possibly solve cases like this. It would take decades to retrain your brain." 

"I'm not exactly thrilled about being in your brain either. I suppose we'll have to pretend to be each other for the time being. We'd get locked up if anyone— Oh, God – Mary." He fell back against the cushions of the sofa. "How the hell am I going to explain this to her?" 

As much as Mary adored Sherlock, she wouldn't want her fiancé to suddenly possess his body. He'd been lucky she'd encouraged him to continue his mad friendship of crime-solving and adventures with Sherlock, but this? This would end it. And that was if she believed them. If she didn't, if she thought the two of them had gone mad, or worse… Tears welled in his eyes and he blinked them away in annoyance.

Why the hell was he crying? He looked over at Sherlock, who quickly looked away. 

"We'll figure something out," Sherlock said, a note of resolve in his voice. "She's… She seems to understand a lot of things. She loves you, and she'll…" He frowned and looked down at his hands.

"Why the hell are you trying to comfort me?"

Sherlock's expression was strained. "I have no idea."

John's stomach rumbled, and the physical sensation grounded him for a moment. The situation was ludicrous, but here he was in this body, and he needed to work with it long enough to get back to his own. Sherlock hardly took good care of himself, so John had a bit of an uphill battle to wage. He sat up again. "When was the last time you ate something?"

Sherlock thought for a long moment.

"That long ago? Well, time to rectify that." John stood and crossed to the kitchen, and opened the refrigerator. It was empty except for a few containers with questionable objects inside. He turned back to look at Sherlock, who was still sitting in John's chair and frowning. There was nothing else for it. "I think we're going to have to go out."

Sherlock turned to look at him. "That's a horrible idea."

"And yet, it has to be done. There's no reason for both of us to go. I'll pop down to the market around the corner and pick up a few things. We've got a long weekend ahead of us if we're going to figure this out."

Sherlock stood. "I don't think we should split up. We should stay together for the time being, just in case that's important."

John considered protesting, but one look at Sherlock made him bite his tongue. Sherlock radiated anxiety, nearly vibrated with it. If John felt out of sorts, he could only imagine how Sherlock must feel about being thrust into a body with a more typically functioning brain. He nodded. "All right." 

Putting on each other's shoes was a strange experience, but even more bizarre was the moment John slid into Sherlock's coat. It even smelled like Sherlock, and he had to close his eyes, nearly overwhelmed. How were they going to do this? What if it was permanent? He'd been happier these last few months than he'd been in ages. His life was finally coming together, and now this had happened to fuck it all up – it was so incredibly unfair.

"Here." He turned to see Sherlock holding out his scarf. John took it and draped it around his neck, and Sherlock gave an exasperated sigh.

"You notice shockingly little, John." He stepped closer and pulled the scarf from John's neck, then folded it in half and went up on tiptoe to loop it around John's neck. 

John stared back at him, reeling at the strangeness of seeing his own face from this angle, of seeing himself the way Sherlock saw him. So many details stood out to him, things he didn't see when looking in the mirror: the tiny lines around his eyes that never quite went away, but intensified in a surprisingly pleasant way when he smiled; the strands of grey in his hair that actually made him look more dignified than he would have thought; the spot on his chin he'd missed while shaving this morning, in his excitement to get dressed and get to the flat.

"There," Sherlock said, though he didn't step back. He stared up at John with an odd expression, one that made John think he was thinking about very much the same thing.

John opened the door. "Shall we?"

They were both silent during the short walk to Tesco's, and neither of them said much as they wandered the handful of aisles. Sherlock seemed content to let John fill the basket, and so he did, planning several meals in his head.

"Excuse me," he heard, and turned to see a young woman pushing a trolley. "Mind if I squeeze through?"

"Oh, sorry." John stepped back. Sherlock, however, remained in the center of the narrow aisle, just staring at her. "Sorry," John repeated, and tugged Sherlock toward him with a hand on his shoulder. 

"Yes, sorry," Sherlock said, and the woman smiled at them both before walking away. 

John started to turn back to the selection of veg, but stopped short when Sherlock didn't follow. John looked back at the woman's retreating figure, and then to Sherlock, whose gaze was definitely tracking the movement of her arse as she walked. She rounded the corner and Sherlock blinked and turned back to him.

"What was that?" John asked.

"What was what?"

"You were checking her out."

Sherlock frowned. "I was not."

John snorted and shook his head – and then looked away as a new thought occurred to him. Sherlock had been the one looking, and he… hadn't. She was attractive, curvy, dark-haired, confident – all the things he so often liked in a woman – and none of it had registered. He looked back to see Sherlock watching him closely through his own dark blue eyes. 

"If you say so." God, it was going to be a long day. Or life. "Want to buy some wine?"

"Yes, I suppose." 

Fortunately, they already knew they had similar tastes in wine, so choosing a bottle wasn't difficult. Slightly more difficult, however, was paying. Sherlock's wallet was organized using a method John could only guess at, and he finally had to hand it over to him to let him find the right card and type in the PIN. The cashier gave them an odd look, but fortunately (for her) said nothing.

Just as they reached the door, it was opened from the outside, and John nearly collided with a man who was coming in.

"Oh, sorry," the man said. He stepped back and held the door open for them, and looked up at John from under a mop of dark blonde hair. 

He looked to be in his mid-thirties and was dressed as if he'd just come from the gym. He wore a long-sleeved shirt that stretched tightly over his broad shoulders, and the muscles in the arm holding the door open had clearly been sculpted through hours with a personal trainer. John's gaze trailed down his lean body before he'd quite realized what he was doing, and when he looked up again, the man was giving him a positively wicked smile.

"S-Sorry," John said, suddenly flustered, and he stepped through the door. Sherlock followed, and they both turned back to watch the man walk through it. He glanced back over his shoulder once and grinned at them before disappearing from sight.

Sherlock cleared his throat and John turned to look at him, but Sherlock only raised his eyebrows before starting down the pavement. John winced. He was usually far more discreet than that, but in Sherlock's body, he didn't have control over it. 

"That was enlightening," Sherlock said after they'd rounded the corner.

"Yes it was." John took a deep breath. "So you—"

"Yeah," Sherlock replied. "And you—"

"Yes." That was far more than he'd expected to reveal in such a short period of time. And the idea that Sherlock found anyone attractive at all was… John glanced at him and Sherlock looked away, as if wanting to look anywhere but directly at John. 

John couldn't really blame him. He exhaled through pursed lips and stared resolutely ahead. They would go back to the flat, and eat a meal, and then put their heads together and figure this damn thing out. And if they couldn't… well, John wasn't going to let himself think about that just yet.

*****

**Notes for the Chapter:**

> [Fanart for chapter 1](http://sherlock-addict.tumblr.com/post/77329972508/my-illustration-to-the-first-part-of-an-amazing) by sherlock-addict.


	2. Two

John set the shopping bags on the table, but Sherlock kept walking, all the way down the corridor to the bedroom.

"I'll just put it all away, shall I?" John called after him. "Wherever the hell I like?" 

As if in response, Sherlock closed the bedroom door behind him, and John shook his head. He didn't even live here anymore, and Sherlock still managed to make him do the housework. Of course, it wouldn't get done at all, otherwise. Mrs. Hudson must help Sherlock far more than she let on. 

He put their purchases away and set about making lunch. Cutting vegetables in Sherlock's body was an unexpected challenge – his hands were larger and his fingers longer, and they didn't feel the same way wrapped around a knife as John's own did. He went slowly and managed not to cut himself, and finally had the makings of a stir-fry.

Twenty minutes later, lunch was finished and on the table, and Sherlock still hadn't come out of the bedroom. John knocked on the door. 

"Sherlock?" There was no response, but that wasn't unusual. John knocked once more, waited a moment, and then opened the door. 

Sherlock sat cross-legged on the floor of his bedroom, surrounded by stacks of books. The wardrobe door was open, revealing even more books inside. He was currently hunched over a particularly large volume, and John was taken aback for a moment by how small he looked. He certainly didn't think of himself that way – was that how others saw him? 

"Could you turn that light on?" Sherlock gestured to a lamp on the bedside table without even looking up from the book. "I had no idea your eyesight was so bad. Have you had it checked?"

John folded his arms over his chest. "There's nothing wrong with my eyesight."

Sherlock snorted. "So you think."

"Lunch is ready."

"Not hungry," Sherlock said, turning the book to look at a diagram from another angle.

"You—" John began, but then let it go. There were many aspects of life with Sherlock that he didn't miss at all.

Five minutes later, Sherlock emerged from the bedroom with a scowl on his face. "I can't _think_ in your ridiculously slow brain. How do you manage to function at all?"

John resisted the urge to flip him off. "I had a light breakfast this morning. You're hungry."

Sherlock scowled. "Oh, for—"

"I get irritable and have difficulty concentrating when I'm hungry." He gestured toward the empty chair across from him. "Sit. Eat. You'll feel better."

Sherlock sat, though his expression remained skeptical. John nodded toward the food on the plate in front of him. How was it that he still had to make Sherlock eat, even though they'd switched bodies?

Sherlock picked up his fork with a put-upon sigh and poked dismally at a salad. "Are these tomatoes?"

"Yes."

"You know I don't like tomatoes."

"But I like them." John raised his eyebrows and Sherlock frowned.

"Fine." He stabbed one dramatically with his fork and shoved the entire slice into his mouth. A moment later, his expression changed to one of disbelief. "This is _good_."

"I know." 

"This is really how they taste to you? Because they taste horrid to me."

"Honestly, Sherlock, you're such a child sometimes." John picked up a tomato slice with his fork and popped it in his mouth, expecting the usual sweet, earthy flavor – and immediately regretted it. The flavor was acrid, bitter, and almost metallic, completely unpleasant. He forced it down and reached for his glass of water. "Oh my God."

"You see?" Sherlock smirked at him from across the table. "I haven't been making it up all this time."

"No, you haven't. Jesus." He winced. "Ugh."

Sherlock flourished his fork. "So what's with all the healthy food, anyway? You never used to cook this sort of stuff."

"Mary's been a good influence."

"Turning forty had nothing to do with it?"

John gave him a scathing look. "I'm a GP, you know. I try to practice what I prescribe." 

Oh God, work: he hadn't yet thought that far ahead. He wasn't due back at work until Monday, but there was no reason to think this situation would be resolved by then. If ever. 

Sherlock picked through the vegetables on his plate, apparently looking for more bits of chicken. "Since I'm borrowing your body for the foreseeable future, I suppose you'll expect me to do the same."

"Yes, please."

"And I suppose you're planning to make sure my body is well fed and rested." Sherlock made a great show of tasting a bit of courgette by taking the tiniest possible bite.

"I am, actually." John straightened in his chair, grateful for the change of subject. "I think you'd be surprised how much better all of the transport works when you consume more than strong tea and the occasional carton of Chinese take-away."

"It's not the transport I'm concerned with." 

John shook his head. "Hasn't everything that's happened today shown you that your brain is _part_ of your body? It's not an independent organ; it requires proper nutrition and care in order to function. If you eat badly and don't sleep, you're not going to be able to use your brain – or mine – to its fullest potential."

Sherlock stared back at him for a long moment; apparently this was a new idea for him. John supposed he shouldn't have been surprised – this was the man who'd deleted the solar system, after all. Sherlock looked down at his plate and started eating again, and John said nothing more. Best not to push too hard at this point. 

"Eat and sleep," Sherlock said at last. "Doctor's orders?"

John plastered on his best _I'm a doctor_ smile. "Yes."

"You're not getting any younger, so I suppose I've little choice."

John ignored him for the rest of the meal.

After the pans were cleaned and the kitchen sorted (with a tiny bit of guilt-induced help from Sherlock), they both dove into the case. 

Sherlock returned from the bedroom with a stack of dusty books and settled at the table to begin thumbing through them. John picked one up and drew his fingers over the worn leather cover, traced the letters of the imprinted title. He opened the book and flipped through several pages. Even the print was an old style, with large ornate initials at the beginning of sections.

"Where'd you get these?" 

"Mycroft," Sherlock replied, not looking up. "He used to collect this sort of thing."

"That's unexpected." John closed the book and set it back on top of the stack. The fact that Sherlock was researching possible supernatural causes for what had happened to them was also unexpected, but then, where else should they begin?

John settled on the sofa with his laptop and began scouring the internet. Everything he turned up indicated that the idea of two individuals' consciousnesses exchanging places was fiction at best, and mad science otherwise. There were websites that described magic spells one could use to perform such a feat, but none that seemed remotely plausible, even if one thought something as ridiculous as magic existed. 

Not that John had a better explanation at the moment. He opened link after link, quickly scanned pages, and found nothing of significance. 

He was able to sort through a large amount of information very quickly, to his great surprise, and all of it was _right there_ , still accessible. He could see an image of each web page in his mind, and he could scan it to locate a passage of interest without having to physically find it again. It was astonishing how much more quickly this happened inside Sherlock's head than his own. He sifted through it all again just because he could, just for the experience of having all of that data in his mind at once, laid out as if on a giant screen behind his closed eyes.

"John? Hello?"

He blinked and turned to look at Sherlock, who was standing in front of him with his hands on his hips. "Sorry. Did you find something?"

Sherlock sat in John's chair with a huff of frustration. "Nothing. Nothing useful, anyway."

"Everything I've read has only convinced me we're both going mad." Even as the words left his lips, he reached for his laptop. "Oh! Why didn't I think of it before?"

"What?" Sherlock nearly leapt onto the sofa to peer at the screen. 

"The case, remember? That was the first place we should've thought to look."

Sherlock's expression switched to annoyance. "I already did. There was nothing more there, just that the man had been hospitalized after being found in the midst of a psychotic episode. He was completely delusional." He stopped and looked at John, comprehension clearly dawning on his face.

"We can probably guess why, can't we? If we assume this same thing happened to him, what would we want to look for next?"

Sherlock was visibly annoyed, but then seemed to swallow it down. "Find out who he was close to, who he might have switched with. And what happened to them."

"Right." John nodded and opened a new window to begin searching. After a moment, he realized Sherlock was being unusually quiet. "What?"

"Nothing," Sherlock replied, but the tone of his voice indicated otherwise. 

John turned to look at him, expecting to see him pouting, but instead Sherlock was staring at him with an expression akin to wonder. He didn't flinch away when John raised his eyebrows in question; he just kept looking, his eyes soft and wide. It was disconcerting to see this expression on his own face, directed at him. He swallowed.

"Okay, you're freaking me out. What is it?"

Sherlock leaned closer and reached up to touch John's cheek, and traced a thumb across his lips. And just like that, John's heart rate increased and his skin began to flush, and oh, this was weird. 

Sherlock's eyes narrowed. "I am incredibly attractive. I had no idea."

John gaped at him for a moment. "You are such a _dick_."

Sherlock tilted his head and reached up to tangle his fingers in hair that John was suddenly aware was not his own. "God, look at me. Have I always been this hot?"

"Are you even listening to yourself?"

"Can I kiss you?"

"You can go fuck yourself."

The corners of Sherlock's lips turned up in the beginnings of a wicked smile, and John felt an unmistakable twitch in his groin. No, no, not going there, absolutely not. 

He broke Sherlock's gaze, only to find himself staring at his lips instead. "I didn't mean it literally."

"This is so bizarre," Sherlock said, still uncomfortably close to John. "I am genuinely sexually attracted to myself."

"You're delusional, do you know that?"

"No, I'm—" Sherlock paused, and his expression changed completely. "I'm you."

John stared back at him, shocked. Of course he was physically attracted to Sherlock, had been for ages, but he hardly gave it a thought anymore. Sherlock had always been off-limits, not interested, not available, and then he'd been dead, and John had moved on. But Sherlock was in John's body now, and he was feeling John's attraction for him full force.

The sound of footsteps on the stairs startled them both out of the moment, and they slid to opposite ends of the sofa. A moment later, Mary's blonde head peeked through the doorway.

"Hello, you two! You weren't answering the buzzer, so Mrs. Hudson let me in below. Having fun?"

"Yes," John said, at the same moment that Sherlock said, "No." 

"I thought you were going shopping with Janine this afternoon," John said, and Mary gave him a surprised look before turning to raise her eyebrows at Sherlock. 

"He's just trying to keep me here longer while he's working on this case," Sherlock said, not missing a beat.

John exhaled slowly, trying to quell the rising panic in his gut. There was no way in hell they were going to fool Mary. He wasn't completely sure he wanted to try, but it was probably their best bet for the time being. No need to frighten her unnecessarily. With any luck, they could sort this out by evening and she'd be none the wiser.

Oh, who was he kidding? This was going to be a complete disaster. She'd think they'd both gone mad, or worse, that they were playing some sort of horrible trick on her, and she'd never forgive them. 

She didn't seem to have caught on that anything was amiss, though. She crossed to the sofa and sat on the arm of Sherlock's chair, and smiled radiantly. Her hair was styled and she was dressed to go out, and – _shit, bugger, and fuck_ – they had plans tonight, didn't they?

"We had to call it short, unfortunately. She got called into work, again." She tilted her head and blinked at Sherlock. "You look different."

"Do I?" His smile was utterly insipid, and John scowled. That wasn't how he looked when he talked with her. Was it?

"It's your hair, I think. If I didn't know better, I'd say someone was running his fingers through it." She winked at John and bit her lip, and Sherlock laughed.

"Don't give him ideas."

"Maybe I should," she said, and leaned down and kissed him. It was a quick, chaste kiss, but John felt the stab of jealousy all the same. Sherlock took her hand and squeezed it, and John had to admit that was exactly what he would have done next. "Are you ready?"

Sherlock smiled up at her. "Ready for what?"

"Drinks with my friends. You promised!"

"I did, didn't I?" Sherlock winced. "Oh, God, I'm sorry. You know how much of an idiot I can be."

John couldn't help snorting at that, and they both turned to look at him. He put on the most disdainful Sherlock-like expression he could muster. "I'm terribly sorry, Mary, but I really do need him tonight. We're in the middle of research on an extremely time-sensitive case, and he's surprisingly useful at this sort of thing."

Mary frowned. "Can't it wait until the morning?"

"It really can't. A man's life hangs in the balance."

"Dramatic, aren't you?" Sherlock muttered.

"Always," John replied. "I'll need him here until very late tonight. In fact, you shouldn't expect him until tomorrow at the earliest."

Mary sighed and turned back to Sherlock. "I suppose I can make your excuses. Again. But you owe me."

"I know."

She turned to John. "And so do you. I don't mind sharing him with you, but once in a while I'd like an entire weekend with him."

"You'll get one," John said. "I promise."

She stood, but Sherlock tugged her hand and pulled her down into his lap, and to John's great surprise, kissed her in a way that was decidedly not chaste. John clenched his jaw and looked away. After an excruciatingly long moment he cleared his throat. "All right, you two. We've got work to do."

Mary had stars in her eyes when she stood up again, and she smiled broadly at both of them as she left.

John fidgeted where he sat, but waited until he heard the outside door close below before rounding on Sherlock. "Was that really necessary?"

"Yes. I wanted to distract her, to set her off enough that she wouldn't get suspicious." 

"Oh, and you think _that_ wasn't suspicious behavior? I don't kiss her like that in front of other people."

Sherlock stood. "You should do it more often. She liked it."

Frustration built in John's throat, and he couldn't push it down. It bubbled up, hot and sharp, and he clenched his fists against his thighs. "You are un-fucking-believable."

Sherlock turned to look at him. "Don't tell me you're jealous of a kiss."

John tried to laugh, but the sound that came out was more like a growl. "I am _not_ jealous, I'm…" He didn't know how to describe it, but it was a sharp feeling, right in the center of his chest.

Sherlock looked as if he wanted to say something more, but stopped himself, looked away. "I'll make tea."

"You never make tea."

"Then it's a day of firsts, isn't it?" 

He walked to the kitchen, and John leaned back against the cushions of the sofa, face in his hands. His head was a mess, and his heart was racing, and God, what he wouldn't give just to be able to shove all of this aside and think about something else. No wonder the decathlete had gone mad. 

As would he, at this rate. Five hours in Sherlock's body, and he was already going round the bend.

Sherlock did indeed make tea, and brought John a cup and the sugar bowl.

"I don't—" 

"Just in case," Sherlock said with a sigh, and settled into John's chair with his own cup. 

John took a sip and winced at the bitterness. After the tomato incident, he probably shouldn't have been surprised. He sighed and added a spoonful of sugar to the cup.

"You'll want another," Sherlock said, not looking up from the screen of his laptop.

John hesitated, but added a second spoonful. The result ought to have been ridiculously sweet, but instead, it was… good. "So what do we know?"

"The victim's name is Paul-Henri Thibaud, twice the French decathlon champion and considered a favorite for the 2016 Olympics. Or was, at least. Two weeks ago he was hospitalized in Toulouse, where he remains." 

John nodded. "So how did you get the matchbox?" 

"Thibaud's brother contacted me and asked me to take the case, and I asked him to send me the mysterious matchbox so I could examine it. It arrived via express post yesterday afternoon."

"And he said nothing else about what happened?"

"Just that Thibaud's wife had recently left him. She accused him of having an affair with his trainer. Which his brother denies with more than a touch of latent homophobia."

"I thought the French were fairly open-minded about that sort of thing."

Sherlock looked thoughtful for a moment, and then frowned at the screen of the laptop. Two minutes passed, long stretches of silence punctuated by bursts of typing, and then Sherlock's smile became smug.

"You've found something?"

"A quick analysis of her Facebook and Twitter accounts seems to indicate that she left not because of his affair, but perhaps because of hers."

"Well, this is getting interesting." John set his computer aside and moved to stand behind Sherlock.

"Her tweets are frequently responded to and retweeted by one Michel Tasse, and he occasionally makes cryptic comments on her Facebook posts as well."

"Michel Tasse," John repeated. "Anything on him?"

Sherlock opened a new tab and typed the name into the search bar. The page filled with references and photographs showing a ridiculously handsome man, late 30s, smartly dressed. Sherlock opened a few pages in new tabs and scanned them quickly.

"D list actor, apparently. Reasonably well known in France, but not much outside the country. He's mostly been on reality shows of late." 

"And he's messaging her publicly on Twitter? Seems a bit conspicuous."

Sherlock shrugged. "Actors do that sort of thing all the time. It gets them attention."

"I suppose it would be a good cover. He flirts with a fan, no big deal."

Sherlock clicked over to another tab. "And here's a photo of them together at a charity event a year ago. Perhaps where they met?"

"They look chummy, don't they?"

"Yes, the body language is very clear. Bodies turned toward each other and slightly closer than might be deemed appropriate for a function of this sort. His hand on her lower back, her cheeks flushed, pupils dilated more than his, and oh, look at that – there's a button undone on her blouse, right in the middle of the shirt, as if she redressed in a hurry and missed it." He right-clicked on the photo and enlarged it, zoomed in on Tasse's neck in the photo. "And there's a touch of lipstick just below his ear that matches the exact shade she's wearing. He didn't wipe it all off."

"Not bad, considering you're borrowing my brain to do all of that."

Sherlock frowned at the screen. "It's a bit slow, but it works."

John flicked him on the back of his neck, and Sherlock swatted him away. 

"So they're both having affairs. What does that have to do with the matchbox?"

Sherlock sighed. "No idea."

John settled on the sofa again – couldn't quite bring himself to sit in Sherlock's chair – and picked up his laptop. "What was Thibaud's diagnosis?"

Sherlock looked up. "His brother didn't say."

"If he switched bodies with someone, he'd certainly seem delusional."

"Right, I'll email him." Sherlock's fingers began to tap rapidly at the keyboard, and then he made a sound of frustration and slowed down considerably.

John suppressed the urge to smirk. "And what about the rest of the thousand-odd matchboxes? What if they're all… magical?"

"Magical? Honestly, John."

"Have you got a better word?"

"The victim's brother claimed to have counted and inspected all of the other matchboxes. I suppose we've no choice but to take his word for it." He paused again. "I'll ask. If he's lying, it should be obvious."

"Perhaps one of those other matchboxes undoes the…" John waved his hands, trying to think of a word that wasn't _spell_. "Thing. And Thibaud was looking for it when he was discovered."

"Perhaps."

They were both silent for a moment. John exhaled slowly, trying not to let himself feel too hopeless. 

Unfortunately, the remainder of the evening was a frustrating series of dead ends, and with each one John felt his anxiety ramp up even higher. By the time Sherlock began reading through seemingly irrelevant social media posts by Thibaud's friends, pacing in front of the fireplace was no longer enough of an outlet. John flopped onto the sofa in exasperation. 

"What if it isn't reversible?" he asked, staring up at the ceiling. "What if we're really stuck like this for the rest of our lives?" 

Sherlock sighed. "John..."

"I'm serious, Sherlock. We need to talk about this. We need to make a plan. At what point do we tell Mary, and Mrs. Hudson? Or Greg? At what point do we give up trying to fix it?"

"I don't know."

"Why don't you know? You always know." John heard the whinge in his voice, but couldn't stop it.

"If only that were true." Sherlock sighed. "It's getting late. Why don't we sleep on it, get back to work in the morning?"

John turned his head to look up at him. "Sleep? Are you out of your mind? How can you possibly think of sleeping right now?"

"Because I'm tired. And staring at the computer screen for the last few hours has only proved to me that you really need a vision check."

"There is nothing wrong with my vision!"

"Wait until you get it back."

"There's no need to worry about that happening anytime soon, is there? Not at the rate we're going."

"All the more reason to sleep then." Sherlock's tone was mock cheerful, and John wanted little more than to wipe it off of his face. With his fist, perhaps.

"I can't sleep until we work this out. It'll drive me mad."

"Well, now you know how it feels."

"To want to murder someone? No. I'm fairly familiar with that one." John immediately winced at the tone of his voice. Normally he was the steady one, the one who kept them focused, but right now he was nearly crawling out of his skin.

"How it feels to be me." Sherlock's smile didn't quite reach his eyes. 

John groaned and looked up at the ceiling. Sherlock was infuriating when he was stroppy, and here John was doing the exact same thing. He had to get out of this room, do something else for a bit. Anything else. "I'm going to take a shower. Try to relax a bit." 

Sherlock watched as John stood and stretched, and then went back to examining the screen of his laptop. 

It somehow took an age to reach the bathroom. John closed the door behind him and leaned back against it for a moment before stepping forward to look in the mirror. The face that looked back at him was ridiculously familiar, impossibly wrong. Was this his new reality? It might be, and Sherlock's sudden calm resolve about the entire ordeal was rapidly becoming infuriating. Perhaps being in John's body was so much easier than being in his own that he wasn't in a hurry to leave. That was a terrifying thought.

He leaned closer to the mirror, close enough to see tiny red veins in his eyes (massive sleep debt in the last few weeks) and the beginnings of lines etched into the skin around his eyes (not so far from forty now, are we?), but no grey yet in that shock of dark curls (genetic lottery there). There were freckles on his nose, ones John hadn't noticed before, and a scar on his forehead, near the hairline. He frowned. Perhaps Sherlock's vision was better than his after all.

He took a step backward and watched himself unbutton Sherlock's shirt, slowly, his gaze following the widening V of skin as it was exposed, pale under the harsh fluorescent light. He shrugged out of the shirt and let it drop, catching it by the collar with his fingertips, the tails dragging the floor, and allowed himself a long moment to look.

There was a dusting of dark hair on his chest, more hair than on John's body, and John raised his free hand, trailed his fingers across his sternum. His eyes were drawn to faint lines on his left shoulder, and he turned to examine them more closely. He drew in a sharp breath and stared, the realization prickling cold at his skin: scars he hadn't seen before, scars Sherlock must have picked up in the last few years. He'd seen scars like these before, on other bodies, in another time. Scars like these were very specific indeed.

He looked away from his reflection and turned to hang the shirt on a hook behind the door. He hadn't asked questions about what had happened in those two years, had preferred to pretend Sherlock had been gallivanting about on an extended holiday. He knew better, though he didn't allow himself to think about it. It opened too many wounds, brought back too many feelings he'd buried, left behind. He didn't want to think of Sherlock's suffering. His own was still too raw, and he wasn't ready to let go of that anger just yet. It was comforting in its own way – solid, secure, grounded. Sherlock would always do shit like that, would always push John away, leave him behind. John could rely on it, and could never forget it.

He started the water in the shower and then unfastened the trousers, pushed them down with the pants, and carefully folded both before turning back to the mirror. He stood completely still for nearly a minute, staring at his reflection, letting his gaze roam. He'd never seen Sherlock completely naked before, despite living in close quarters with him for more than a year. And though Sherlock had predicted it, there was nothing particularly disappointing about his penis. It was completely ordinary. John supposed that in itself ought to have been surprising.

The water had grown warm now, and he stepped under the spray. Happily, this felt just as good in Sherlock's body as it did in his own, and some of his tightly-wound tension began to seep away. He washed his hair – though it was still difficult to think about this mop belonging to anyone other than Sherlock – and soaped himself up, and then stood with his face turned up into the spray. It was so bizarre to be taller, to be differently-shaped, to be literally in someone else's skin. 

He slid his hands over his chest, rinsing away the rest of the soap, and then down to his thighs, and _oh_ – that was interesting. He had the beginnings of an erection, just from that touch. He kept his eyes tightly closed and tried very hard not to think as he wrapped fingers around his – Sherlock's – no, _his_ penis and gave it a long, slow stroke. It felt different, not like touching himself at all. He opened his eyes and looked down, watched long fingers slide slowly along the shaft. In his own body, he'd be completely hard by now, just from the anticipation of jerking off. He'd come dozens of times standing in this exact spot, biting his lip to keep quiet, one hand against the cool tile wall, pulling hard and fast. Sherlock would often smirk at him afterwards, and John would fantasize about creative ways to wipe that smirk off of his face. And just like that, he was fully erect. 

Another long, slow stroke, and different sensations rippled through his skin, sparks behind his eyes, and _oh God_ , this was—

This was not what he should be doing. He dropped his hands to his sides and looked up at the ceiling. With any luck, they'd find a way out of this, and he'd have to look Sherlock in the eye again, with the knowledge of exactly how to make him come, and that – no, that wasn't… no. 

He turned the temperature of the water down until he had to grit his teeth.

He dried off and redressed, and didn't look in the mirror until Sherlock's body was covered up again. He ran a hand over the stubble on his chin (tomorrow) and combed that mop of hair away from his face. He looked harder now, less like Sherlock, and there, that was better. Back to work.

He opened the door to see Sherlock passing by, on his way to the bedroom. 

"They're on the mantel."

John glanced at the mantelpiece and then back to the open bedroom door. "Sorry, what are where?"

"Cigarettes."

John's eyebrows shot up. Of course – he'd been experiencing nicotine cravings. It explained quite a lot. He crossed to the bedroom door. "I'm not smoking a cigarette for you."

Sherlock pulled John's shirt off and dropped it to the floor. "I always like a cigarette after a wank in the shower."

John's mouth opened, but no sound came out for a full second. "I did _not_ wank in the shower."

Sherlock turned to look at him, and then shrugged. "You should've done. You'd sleep better."

"I'm working under the assumption that I'm borrowing your body for a short time. Performing a sexual act on it without your permission seems pretty damn inappropriate."

Sherlock stepped out of John's jeans and kicked them aside. "Oh, for fuck's sake. You've spent the day in my body, and you've eaten, pissed, farted – masturbation is just another normal bodily function." He looked down at John's underpants and frowned.

"Do us both a favor and leave them on." John sighed and leaned against the doorframe. "I still don't know how you can sleep right now."

"Isn't it glorious? This is one part of being in your body I plan to enjoy." He tugged back the duvet on the bed and slid into it with a happy sigh. "Is this all right, or would you prefer the other side?"

"I… sorry?"

"Or don't sleep, if you like, but you should know I only slept three hours last night, so you're due."

"You want me to sleep here? With you?" John felt his face heat: Sherlock was capable of blushing after all, it seemed. It was a good job the lights were dim in here.

"The upstairs bedroom no longer has a bed, and you know how wretched the sofa is to sleep on." Sherlock paused and looked up at him. "It's not as if it's the first time we've shared a bed."

John looked away. "That was different. We were out of town for a case. This is all just… weird."

"Yes, it is. Pyjamas are in the top drawer if you want them. I usually sleep naked these days, though."

John closed his eyes. That was definitely a bit of information he didn't need at the moment. Pyjamas, then. He stripped off Sherlock's clothes, leaving them in a pile right next to his own on the floor, thank you very much, and pulled on pyjamas that were softer than anything he could remember having on his skin in a long time. 

He switched off the light and made his way to the bed in the darkness. He'd never so much as sat on this bed before now. The mattress was a bit firmer than he preferred – in his own body, at least. All bets were off at the moment. He turned onto his side facing away from Sherlock and tried to relax, but the events of the day spun in his head, replaying themselves, new details standing out each time. He couldn't quiet his mind for more than a few minutes, and it was infuriating.

Worst of all was the soft rhythmic breathing next to him – in John's body, Sherlock was having no difficulty sleeping. Half an hour went by, and then it had been a full hour, and then the clock on the bedside table read 1:00. He was exhausted, but unable to lull himself to sleep. 

He finally sat up and picked up his phone. Maybe a mindless card game would help. Or a book – he had some stored in his Kindle app. 

Sherlock shifted next to him. "S'matter?"

John sighed. "I can't turn your brain off."

Sherlock made a chuckling sound. "M' not having that problem."

"Some advice would be helpful, you know."

"Should've had a wank in the shower."

John closed his eyes. "Anything else?"

Sherlock turned toward him and snuggled under the duvet. "Turn off the phone. The light will interfere with your body's melatonin production. Try thinking about something repetitive and tedious, like counting as high as you can in another language or reciting the elements in reverse order of atomic number."

John looked down at him, at his own face pressed into the pillow. It was going to take a very long time to get used to seeing Sherlock this way. "I'll try."

Sherlock yawned. "And if that doesn't work, get up and do something useful."

John couldn't help but smile. "Go back to sleep, Sherlock." He switched off the phone and settled on his back in the darkness, and focused on remembering how to count in French. He got to two hundred before he finally drifted off.

*****

**Notes for the Chapter:**

> [Art for chapter 2](http://sherlock-addict.tumblr.com/post/77415633535/a-scene-from-an-amazing-fic-inexplicable-so-what) by sherlock-addict.


	3. Three

"John."

Something poked him in the side, and John groaned. No, it was Sunday, wasn't it? He didn't want to get up yet, was exhausted, and he'd had one hell of a—

"John, wake up."

A very familiar voice, from right beside him in the bed. After an initial moment of complete disorientation, the events of the previous day flooded his mind. That was _his_ voice, but coming from Sherlock. Oh, God.

"No, don't want to." He pulled the pillow over his head. Maybe if he went back to sleep, he could forget about it for a bit longer. He wasn't ready to face it just yet.

"You need to deal with this, John."

"Deal with what?" 

Sherlock yanked the pillow away from John's head. " _This_."

John opened one eye and squinted at him. "What are you on about? What time is—oh my God."

Not two feet away from him, right at eye level, was a very erect penis. His own, in fact, though he'd never quite seen it from this angle before. He pulled the duvet back over his head.

"I'm going to pretend I didn't see that."

"Oh, for—" Sherlock pulled the duvet away again. "It's your penis. You need to deal with it."

John huffed out a laugh. "And how exactly do you expect me to do that?" Sherlock gave him a long look, and John shook his head. "You could just wait for it to go away. Or go have a wank in the bathroom. Easy."

"I would have done, but you said last night that it would be inappropriate for us to masturbate while in each other's bodies."

"So don't masturbate."

Sherlock groaned. "But I want to. Right now. I don't know why. It's not normally such a…" He paused and seemed to wrestle with his frustration for a moment. "You have a stronger libido than I do. God, the dreams I had last night."

John smirked. "Oh really?"

"John…" Sherlock's voice had taken on a whinging tone.

"I give you permission to masturbate while in my body. All right?" He pulled the duvet back over his head. With any luck, he could go back to sleep for a few hours.

Sherlock heaved a dramatic sigh and said nothing more. Just as John began to drift back to sleep, he became aware of movement on the bed. Rhythmic movement, in fact. 

John opened his eyes under the duvet, incredulous. "I didn't mean for you to do it here!"

"Shut up," Sherlock said, slightly breathless now. 

John tried not to listen, tried to think about anything else, but he was finally unable to help himself. The idea of Sherlock as a sexual being was still a very new one, and the thought of him sitting a few feet away, pulling himself off – or actually, pulling John off… John clenched his jaw. It shouldn't be that hot, but it was, and he was getting hard himself just thinking about it.

He resisted for nearly a minute before he finally let go, let his fingers wrap around his own growing erection. He teased the skin and felt the shaft harden beneath his fingers. It felt so different in his hand than his own penis did. He wasn't sure what Sherlock liked, what sort of strokes would build it up, keep him hanging on the edge for as long as possible, and then finally push him to climax. Masturbation wasn't something he'd had to give much thought to in thirty years. It was just something he did, sometimes slow and relaxed, sometimes quick and efficient, but always easy – until now. And wasn't that a strange thought? 

Sherlock moaned softly through closed lips, and John made up his mind. He pushed the duvet back and sat up, and leaned back against the headboard next to Sherlock.

"Mind if I join you?"

Sherlock kept his eyes tightly closed. "Oh, yeah. I mean, no, I… please."

"Right." He looked over at Sherlock and for a moment watched the bizarre show of himself aroused and jerking off. God, did he really look like that?

It was a bit too weird, and so he let his gaze drift down again, down to where Sherlock's cock jutted up from his groin. It wasn't much smaller in length than his own, though the girth was different enough that he had to try several grips before finding the one that worked best. Sherlock had a looser foreskin than John did, enough to pull it up and almost completely over the glans. That was a different sensation, and he found he enjoyed it. Oh, a lot, actually, _Jesus_.

"Like that, but faster," Sherlock said. 

John's breath caught. He couldn't look at Sherlock, couldn't bear to see his own face with such a look of heat and longing on it, directed at this body, at Sherlock's body. He closed his eyes and nodded, and said, "All right."

Only, he didn't actually say _all right_. He'd intended to, but somewhere between his (Sherlock's) brain and his (Sherlock's) mouth, it turned into, "Show me."

Sherlock didn't question him, didn't hesitate. A second later there were smaller fingers covering his, showing him what to do, leading him, and _oh God_ it was the hottest thing he'd experienced in a long time. Within a minute, Sherlock pushed his fingers away and took over, and John didn't stop him, didn't want to. It was Sherlock's body, after all, and even if it was John's hand, it wasn't really like Sherlock was giving him an incredible hand job right now, with the duvet tangled around their legs, in Sherlock's bed and _oh God oh God_ he was going to come.

"Yes, there, just… oh, fuck…" 

The orgasm felt different than his own, brighter somehow, more intense, but shorter; it burned out quickly and left him gasping, fingers still clenching the duvet.

"Oh my God," he said, and opened his eyes to the bizarre sight of his own face staring back at him, flushed with desire and arousal. No, not his own – it was Sherlock looking at him this way, Sherlock whose eyes were dark and desperate and uncertain. John let his gaze drift down to where Sherlock was still hard and leaking, and for one brief second he felt an impulse to do something very reckless indeed. But no, not that, not right now, not in someone else's body like this – but how interesting that it seemed so easy at the moment, so natural.

Instead, he closed the space between them and took Sherlock's (his) erection in hand. Sherlock's eyes fell closed and he exhaled shakily, and John decided right then and there to make it as good as he possibly could. He took his time, watching Sherlock, watching for signs he knew well, even if he'd never seen them from this perspective, and adjusted his strokes, altering pressure, speed, circling his thumb to slow things down, and then pulling hard and fast through the ring of his thumb and forefinger. He brought Sherlock to the edge and pulled him back, and then did it again, which earned him a few choice insults. This would be amazing, though; it was the way he did it when he had half an hour and a long bath and had just watched some fantastic porn that he could replay in his head. This was how he had sex with himself, and he'd never shared it with anyone, not even Mary. 

Sherlock was shaking by the time John finally let him come, one hand stroking quickly over the head, squeezing just so, and the other tugging at his balls, pressing a fingertip firmly up against the skin just behind. He could see it, could see the moment when he tipped over the edge, and from there it was all about maintaining pressure, riding it through. Sherlock grabbed a pillow and pressed it over his face, muffling his shout, and John didn't let go until Sherlock collapsed against the mattress, tension wrung out of his limbs. 

It took less than a minute for John to come to his senses: there was semen on his hand and on the sheets, his and Sherlock's, and _oh God_ , what had they done?

"Stop thinking," Sherlock said to his left, and John looked over at him. "You look like you're about to have an anxiety attack."

John's insides twisted and he made a sound like a laugh, though the situation wasn't funny at all. He shook his head and forced himself to look at Sherlock. "We just had sex. You and me. Give me one good reason not to panic about that." 

Sherlock's expression looked pained. "We don't have to call it sex."

"We brought each other to orgasm. What else would you call it?"

"It was a mutual wank. Schoolboys do it all the time."

John gave him a long look. "No, they don't."

Sherlock waved his hand in a vague _what-the-fuck-ever_ sort of gesture.

John flopped back down on the bed and pulled the duvet over his head again. "Oh my God. I've just cheated on my fiancée."

"With yourself. I've a feeling she wouldn't blame you for that."

"You make a fucking horrible conscience."

Sherlock sighed. "God, am I always so dramatic? It's far more ridiculous than I realized."

"Not that it matters. Once we tell her about this whole switching bodies thing, she'll think we've both gone mad and it will all be over anyway." John pulled the duvet from his face and stared up at the ceiling. 

It was true, wasn't it? This was utterly mad, impossible, and Mary wouldn't be able to get past this. She loved him, but she wouldn't be able to accept him like this, in someone else's body. He felt something twist in his belly, sharp and cold.

Sherlock was quiet for a moment, and John had the distinct impression he was trying to think of something to say.

John pressed a hand against his forehead. "Errgh, just don't, all right?"

"Don't what?"

"Try to comfort me."

"I thought I just did." Sherlock swung his legs off the bed and stood, stretching. John caught a much-too-vivid glimpse of his own bare arse before he looked away. "Stop whinging. Go make breakfast."

John tugged the pyjama pants back up over his hips, and then stopped, annoyed with himself for complying so quickly. "A 'please' would be nice."

"Would you like a kiss as well?"

John turned to look at him, eyebrows raised. "Despite what just happened, the idea of kissing myself is just… bizarre."

"Agreed." Sherlock fished John's clothes from the floor and folded them carefully.

Breakfast, then. John plucked one of Sherlock's dressing gowns from the hook on the back of the door and wrapped it around himself, then ducked into the bathroom for a quick piss and wash-up. If a day ever called for ridiculous amounts of coffee, this was definitely it. And then eggs and toast. He yawned as he dried his hands, and then headed to the kitchen. If he was still in Sherlock's body tonight, he was going to take a sleeping pill.

"Good morning, dear!" 

John whirled around to see Mrs. Hudson setting out tea on the sofa table. She smiled at him, and oh God, he'd hoped he wouldn't have to face anyone else they knew so soon. He smiled back reflexively, realized he was doing it and wiped it off his face a bit too quickly, and then tried a moderately pleased expression. 

"This is lovely, thanks."

She beamed at him. "You're in a pleasant mood this morning, aren't you? Not stroppy as usual."

"Ah, yes. Sorry." Sherlock in the morning was not particularly pleasant. How had he forgotten a detail like that? Mrs. Hudson looked unusually bright-eyed herself this morning, as if she'd been awake for a while, and there was an extra bounce in her step that he had only seen when… Ah, of course. "How was your date?"

She smiled and swatted him on the arm as she walked back to the kitchen. "That's none of your never-mind. What did you get up to last night?"

Right on cue, the bedroom door opened and Sherlock strolled out, wearing only John's boxers. He yawned and crossed straight to the tea Mrs. Hudson had laid out. "Good morning."

John closed his eyes for a full second, steeling himself. He opened them again and turned to look at Mrs. Hudson, whose face had gone rather pale. 

She pressed her hands against her rapidly flushing cheeks. "Oh, goodness, you…" 

"It's not what it looks like," John offered.

Sherlock snorted from across the room. "Unless it looks like we just had a mutual wank, in which case it's exactly what it looks like."

"Oh!" Mrs. Hudson spat, and glared at Sherlock for a moment before seeming to make up her mind. She crossed to where Sherlock was standing and wrung her apron in her hands. "You listen to me, John Watson! If you think I'm going to stand by and say nothing while you run around on Mary, you'd best think again." She stepped closer, and lowered her voice to a harsh whisper. "And with Sherlock, knowing how he feels about you? It's just cruel, John. I thought you were a better man than that."

With that, she turned and walked away, heels clacking against the wooden floor.

John stared after her, unable to keep himself from gaping in her wake. He turned back to Sherlock, who looked stricken, and then closed his eyes again. 

Coffee. He couldn't possibly face this without coffee. He turned to the kitchen, his mind whirling. Less than twenty-four hours ago, he hadn't been sure Sherlock was capable of feeling attraction or desire – definitely not romantic love, and certainly not for him. 

What if Sherlock was capable of all those things? What did that mean? What did John want it to mean? 

"John," Sherlock said, and there was a tone of warning in his voice. It was a full second before John realized that something was wrong.

It took three steps for John to reach his side, and they both stared down at the sofa table in disbelief. There was a small pile of matchboxes now, each identical to the one Sherlock had opened the day before.

"Bloody hell," John muttered. He'd never been more grateful for the change of subject. "Where did they come from?" 

"No idea." Sherlock scanned the table quickly. "There are… God, I need coffee. Or a functional brain. Maybe fifty." He picked one up and turned it over in his fingers. "All identical to the original as far as I can tell."

John ignored the jibe. "That's not possible. They can't just have appeared out of nowhere."

"And yet, that seems to be precisely what happened."

John squatted down to stare at the matchboxes. "Seriously, Sherlock. This is fucked up beyond anything we've seen before. I don't have a clue where to—" He paused and looked up. "How many did you say the victim was found with?"

"One thousand, eight hundred and twelve."

"So apparently they reproduce."

"Inanimate objects don't normally reproduce, John."

"Of course they don't, but what's the alternative? Someone broke in and dumped a bunch of identical matchboxes right here, just to fuck with us?" 

Sherlock flung a matchbox against the fireplace; it skittered off and disappeared from sight. "Fuck it all, this is not what I was expecting."

"Shut up a minute, will you? Eighteen hundred and twelve, what does that mean?" 

"There were quite a few wars in 1812."

John frowned. "No, too obscure. If the boxes are replicating, they're doing so at a particular rate. We started with one yesterday and now we've got fifty. It hasn't been a full day, more like eighteen or twenty hours, maybe less. Suppose they keep going like that, with fifty more every eighteen hours or so."

"At that rate it would take…" Sherlock squinted, clearly trying to concentrate.

"Twenty-seven days," John said, and then blinked. "Wow." He'd never been able to do maths in his head that quickly before.

Sherlock sighed, clearly annoyed. "So just a few weeks until we'd have 1812, assuming a linear rate of replication. We need to find out what happened to Thibaud during the month before he was found."

John picked up a matchbox and slid the cover open, but nothing happened. It was empty. He felt a fresh wave of despair. "And then what?"

Sherlock sank to his knees on the floor. "Look for clues. Duh." He picked up another matchbox and examined it closely. "This isn't a brand I recognize."

"I looked it up last night, actually. It's very obscure, but I found a few mentions on some pipe smoking forums. The company that manufactured them seems to have gone out of business around 2000."

Sherlock frowned. "British?"

"Yes."

"They might've been manufactured in-country, then. Perhaps we should pay a visit to the factory."

John opened his laptop. "I'm on it."

*****

"This can't be right." Sherlock frowned at the boarded-up shop, most recently a music vendor. "A factory on this part of Charing Cross Road?"

John shrugged. "Maybe some shopfronts were combined, or split? The number isn't even here."

"Is it somewhere else along this stretch? Numbering isn't exactly consistent in this part of London."

John turned and looked up and down the street. "No idea." He turned back to Sherlock, but something caught his eye above Sherlock's head, a shadow with a strange shape, out of place on a commercial street. He looked directly at the spot, but there was nothing there. He frowned.

"What?" Sherlock looked up.

John blinked, looked away. "Nothing. Just… thought I saw something for a moment."

"We should ask the neighbors." Sherlock indicated an ancient-looking bookshop next to the empty music store. "This looks as if it's been here for at least that long."

John glanced up at the doorway, his brain taking in the details: the peeling paint around the doorway, the tarnished edges of the street numbers on the door, the imperfections in the glass window. "Yes, at least." 

An old-fashioned bell rang when Sherlock pushed open the door. The shop smelled of dust and old books and peppermint, and it appeared to be empty. They wound their way towards the back, through a maze of towering bookshelves. The shop seemed far more expansive than one would expect from the outside, but there was no attendant in sight.

John looked around. "Maybe they stepped out?" 

"Good morning," they heard, and turned to see a woman standing right behind them. She'd been exceptionally quiet – they hadn't heard her approach at all. "How can I help you?"

Sherlock stared hard at her, but John's brain was already cataloguing details: middle-aged (but maybe older than she looked), eclectic dress (former hippie?), new grandmother, expensive earrings (antique, heirloom). 

"Yes," John began, and paused to glance at Sherlock, who nodded. "We're actually looking for information about a factory that was along this street until about fifteen years ago. Do you happen to know anything about it?"

The woman looked surprised. "Can't say I've ever heard mention of a factory around here. Not one in recent times, anyway. What sort of factory?"

"It produced matchboxes, for one thing. Perhaps the matches themselves as well. We aren't sure."

She frowned and looked back and forth between them. "Did the manufacturer have a name?"

"Just 'W' – perhaps an initial? We found an address on this street, but that number doesn't seem to exist."

She looked surprised for a brief moment and then schooled it away again. "W? That does sound familiar. Do you happen to have this matchbox with you?"

Sherlock fished into his pocket and pulled out one of the matchboxes. She took it from him, an odd look on her face. 

"Well now, I haven't seen one of these for quite a while." She turned it over in her fingers and examined it carefully. "How did you come by it?"

"A friend gave it to me," Sherlock said. "Is it valuable?"

Something flickered across the woman's face. "An empty matchbox? Hardly."

"How did you know it was empty?" Sherlock asked.

She shook it slightly and raised her eyebrows at him. "These were once quite popular, but so few people smoke these days. At least, not in public. And so much manufacturing has moved to China of late. I suppose the company folded."

"Perhaps. It's in remarkably good condition for something more than a decade old, don't you think?" 

"Yes." She didn't look away from Sherlock, kept her gaze locked on his.

"Well, thanks," John said, and tugged at Sherlock's sleeve. 

Sherlock plucked the matchbox from her hand and gave her a terse smile, and they both turned to go.

"I'll think on it," she said as they neared the door, "and let you know if I remember anything else. How should I contact you?"

Sherlock turned around. "He's Sherlock Holmes." He nodded his head to indicate John. "Google him if you like."

"I will," she replied.

The bell jingled again as they stepped out onto the street and they both started down the pavement at a brisk pace.

"That was a bit creepy," John said after a moment.

"I agree." Sherlock looked back over his shoulder. "She certainly tried hard to pretend it was just an ordinary matchbox."

"Curiouser and curiouser," John muttered. "Now what?"

"Are you hungry?" 

John glanced sidelong at him, surprised. "I suppose." 

"Then let's get lunch and mull it over." Sherlock held up his hand to hail a passing cab, but it rushed past them. "Can we please have something loaded with salt and fat?"

"Only if you promise to take my body for a run this afternoon."

Another cab passed them by, and Sherlock scowled in frustration. "A bit of help, here?"

"Not a chance. I'm enjoying watching you try to get by without your magic powers."

Sherlock sighed. "Fuck it, let's walk. I know a good spot for fish and chips about half a mile away."

He started down the pavement, and John took great delight in only needing a few steps to catch up, instead of his usual trailing jog. 

"Nice to see you having regular meals for a change." John couldn't help a smug smile.

"It's strange to feel hungry. I've spent years learning to ignore the sensation. It's almost…" He trailed off as two young women passed them on the pavement, arms linked and laughing together. Sherlock turned around and walked backwards in order to watch them walk away. 

John grabbed his arm and tugged him back around. "Could you be a bit less obvious?"

Sherlock looked back over his shoulder at them. "Did you see how short her skirt was?"

"I didn't. Engaged now, remember?"

Sherlock leaned in close and whispered. "And yet you thought about sucking my cock this morning – remember?" 

"Jesus, Sherlock!" John glanced around, but no one was close enough to have heard. He lowered his own voice to a whisper. "How the fuck do you know that?"

"You've full access to my brain. I suggest you use it." 

"I'm definitely trying," John muttered.

They turned a corner and Sherlock nearly collided with a dark-haired man in a sleek suit, who was tapping at the screen of his phone as he walked. 

"Shit, sorry," the man said, and he continued on his way. 

"No, my pleasure," Sherlock replied, and the man turned back to grin at him before walking on. Sherlock stared after him, mouthing the word _wow_.

"Oh, for fuck's sake." John walked on, shaking his head, and Sherlock had to jog to catch up.

"This is fascinating." 

"If you're about to deduce some shit about my sexuality, I'm not listening."

"I'm in your body, John. It's unavoidable at the moment. Surely you're doing the same."

"I'm actually not. I'm far more worried about how Mary is going to react to all of this if we don't get switched back soon."

"So you keep saying." John turned to glare at him, and Sherlock shrugged. "It's fairly obvious that you're sexually attracted to a broad range of people. That's not going to disappear just because you've picked the one you're planning to fuck for the rest of your life."

"How romantic." John turned to look at him. "I've never heard you swear this much in all the years I've known you."

Sherlock wrinkled his nose. "I'm not even trying. It just comes out."

John couldn't help smiling at that. "Choosing a partner is about far more than sexual attraction, you know."

"I know," Sherlock said, and looked away.

They were quiet the rest of the way to lunch, and John pondered exactly how much Sherlock knew about his feelings for Mary. And for Sherlock, for that matter.

***** 

"Well, that was a waste of an afternoon," John muttered. 

The taxi crawled through surprisingly heavy traffic, and John was getting more antsy by the minute.

"I wouldn't say that." Sherlock didn't look up from the screen of his phone. "We located someone who had seen the matchboxes before, and she dismissed them as unimportant in a suspicious manner. That generally suggests foul play is a possibility. And I didn't have to eat a single vegetable for lunch."

"You had chips."

"I'm not six years old; I know they don't count. Aha, Thibaud's brother responded." There was a pause as he scanned the email. "He reports that he wasn't aware of anything out of the ordinary, other than the breakup."

"Dead end?"

Sherlock frowned. "The ex-wife is the most likely suspect. She found out her husband was having an affair with another man and took her revenge."

"With a magical matchbox?"

"Hell hath no fury like a woman scorned." 

"I suppose." John swallowed and looked out the window again. That hit a bit close to home.

"Oh, look, she just accepted my Facebook friend request. Perfect timing."

John blinked. "You have a Facebook account?"

"Of course I do. It's quite useful. Humanizes me, apparently. I'll send her a message and ask if she has any information about what may have happened to her ex-husband."

"If she's the one behind it, will she actually tell you anything useful?"

"She'll overcompensate and give me far too much information. Honestly, John, have you learned nothing from me?"

John responded with a rude gesture, which Sherlock ignored. 

He almost tripped over his own feet getting out of the taxi; it was strange to have longer legs to contend with. Sherlock didn't seem to be struggling with the adjustment to John's more compact body, damn him.

Mrs. Hudson was going out when they came though the street door, and she gave them both a sharp look. John couldn't meet her eyes, but Sherlock smiled and held the door for her, and wished her a pleasant afternoon. John was shocked for two full seconds until he realized that was indeed what he would've done.

He had a fascinating view of his own arse on the way up the stairs, which led to some interesting sparks of arousal. It was surprising just how sexual Sherlock actually was, far more than John would have previously suspected. He'd learned today that Sherlock was obsessed with the back of John's neck, at least judging from the bizarre impulse he'd felt to lick it every time he had a good view. And that didn't begin to touch on the flight of butterflies that took off in his midsection every time Sherlock (John) smiled broadly at him. He'd have to be more conscious of that in the future – at least, if he ever got his own body back. 

Sherlock opened the door of the flat and then stopped so suddenly that John crashed into the back of him. 

"What the—" John began, and then saw what Sherlock was looking at. The pile of matchboxes had grown even larger in their absence, had perhaps doubled in size. There were matchboxes all over the floor, scattered as if they'd spilled out all at once. 

Sherlock crossed to the table and stared down at them. "Not linear, then."

"Which means we're looking at having a couple thousand in a few days, rather than a few weeks." John dropped to his hands and knees and crawled under the sofa table to retrieve the matchboxes that had fallen there. "Maybe they only replicate when we're not looking?"

Sherlock made a sound like a strangled laugh, and John rolled his eyes. It was a plausible theory, surely? As plausible as anything could be at the moment, anyway. He gathered up the matchboxes one handful at a time and heaped them into one large pile on the table. Sherlock was sitting in John's chair and watching him thoughtfully, his jacket draped across his lap. 

"It is a possibility," John said, unable to keep the annoyance out of his tone.

Sherlock's expression was unusually blank. "What is?"

"That they replicate only when we're not there to see it."

"Yes, of course." Sherlock cleared his throat and looked at the pile of matchboxes again. "One hundred, do you think?"

"At least. Let's do a proper count." John gathered up a handful of matchboxes and dropped them onto the jacket in Sherlock's lap. "You do those."

Sherlock's expression was one of carefully controlled exasperation. "Honestly, John—"

"Oh, not enough of a challenge for you?" John smirked and dropped another handful on him, and then another, enough that they began to spill off of the jacket and into the cushions of the chair.

Sherlock clenched his jaw. "John—"

John grinned and threw another few matchboxes at him; one dinged him squarely in the chest. Sherlock shook his head and looked away again, and John realized he'd missed something. Before he could look closely enough, Sherlock brushed the matchboxes off the jacket and onto the floor, where they rained down on his feet. 

"Thirty-seven."

John snorted. "Bullshit."

"They make a very distinct sound when they hit the floor. Count them yourself if you don't believe me."

John shook his head, but moved closer and gathered up the matchboxes at Sherlock's feet. Some had skittered under the chair and others to the side. He picked them up four at a time and yes – there were indeed thirty-seven. Despite his complaints, Sherlock was apparently doing just fine in John's brain. 

John looked up to tell him so, and realized a moment too late that his head was between Sherlock's knees. Sherlock stared down at him with a dazed expression, still clinging to that damned jacket. John's gaze drifted down to it, and back up again. Why was he so determined to hang onto it when— _oh_. John raised his eyebrows.

Sherlock groaned and looked up at the ceiling. "This is unbearable. How do you deal with it?"

"Deal with what?"

"This constant barrage of sexual impulses. My God, John, is it all you ever think about?" He finally pulled the jacket from his lap, and John's gaze shifted to the rather large bulge at his groin. "I would have noticed if you constantly had an erection around me, so you must be able to control it."

John swallowed down the impulse to lean forward and cover that bulge with his mouth, and forced himself to look up again. Sherlock was hardly suffering alone in this, but John reckoned it would do him little good to point that out just now. Sherlock slid down in the chair, knees falling open, unconsciously moving said erection even closer to John, all while looking completely miserable. 

John took a steadying breath. The best way to deal with a pouting Sherlock was a full-on challenge. "I learned to control it when I was sixteen. Didn't you?"

Sherlock glared at him. "Of course I did. Your body is not cooperating."

John ought to have been mortified that his body was behaving so badly for a guest, but he wasn't quite sure what he was feeling at the moment. It was all a mash of Sherlock's body's responses and his own emotions, and none of it was clear. It was a bit of a wild ride – and even wilder for Sherlock, apparently. 

But what had triggered that sort of response in John's body just now? _Ah_ – of course. He couldn't stop a sly smile from spreading across his face. "Doesn't mean it never happens. Particularly when I have a nice view of your arse." 

"That is blindingly obvious to me now."

"But I don't usually get that hard." John's gaze shifted back to Sherlock's groin, to where he could see the outline of his erection even through denim. It did look larger than one might expect, now that he saw it from this perspective. Heh.

"For fuck's sake, could you get off the floor now?" Sherlock's voice wavered a bit, and he looked up at the ceiling again, as if the sight of John on his knees was just too much to bear.

John scooted backwards and leaned against Sherlock's chair, stretching out his legs in front of him. "How do you usually deal with it? In your own body?"

Sherlock opened his mouth and closed it again, and then seemed to force himself to look at John. "If it gets to this point, I usually go have a wank in the shower."

Memories flashed across John's mind now, of all the times they'd come back to the flat after solving a case, high on the adrenaline of it all, when Sherlock had headed straight for the shower. He chuckled. "That explains a few things."

Sherlock stood, awkwardly. "I think I'll just…" He gestured towards the bathroom.

"Right." John's mouth was suddenly dry. "I'll—" _help you_ , Sherlock's brain quite cheerfully suggested, but he caught himself this time. "—count these." 

He looked down at the matchboxes scattered on the floor and tried very hard not to think about the fact that Sherlock was going to stand under the spray and stroke himself off – stroke John's cock, to be precise – while thinking about his (Sherlock's) arse. He'd done that himself more times than he cared to count, and in that very shower. 

The bathroom door closed and the shower started, and John groaned. He wanted to get up off the floor, walk right over to that bathroom, and _do_ something. Get into the shower fully clothed, drop to his knees, and offer to take care of the problem himself. Right now, in this moment and in this body, and despite what he'd said just hours ago, he wanted it. How much of that was what Sherlock wanted, and how much of it was _him_? 

It was nearly overwhelming, the most powerful sexual desire he'd experienced in ages, and right now it was compounded by the fact that Sherlock was naked and wet, and just on the other side of that door. He'd even left it cracked a bit, perhaps in invitation. Before he was quite aware he'd done it, John was on his feet and halfway to the bathroom. 

The door buzzer sounded. He stopped, closed his eyes, and tried to decide what to do. It could be a client. Neither of them was up for a case right now; they'd only send the person off anyway. No need to answer the door. 

The buzzer sounded again. Determined, whoever they were. It was Sunday, so no deliveries were expected. Mrs. Hudson would get it in a moment – ah, no, she was out. John groaned and pressed a hand over the erection straining against the fabric of his trousers. He crossed to the window to peek out, and his heart sank almost immediately.

Standing on the doorstep, wrapped up in a fluffy pink scarf and raising her finger to press the buzzer once again, was Mary.

*****


	4. Four

Mary. Oh, God.

Once the flash of panic passed, John was nearly overwhelmed with a flood of conflicting emotions. At least it helped wilt his erection – Sherlock's trousers left so little to the imagination.

He made his way down the stairs as she pressed the buzzer once again, and dredged up his best annoyed-Sherlock expression before he opened the door. "What are you doing here?"

She looked mildly taken aback. "And a lovely day to you as well. Came to retrieve my fiancé. If you've finished with him, that is."

"I'm not, as it turns out. I may need to keep him for the foreseeable future." He stepped back and motioned her through the door. 

"Should I be jealous?" She winked at him and headed up the stairs. 

Should she be? Jesus, that was a loaded question. John took a steadying breath and followed.

She slid out of her coat and scarf and hung them by the door. "Where is he?"

"Taking a shower." 

She tilted her head and frowned. "A shower? In the middle of the day?"

John clenched his jaw. It was, now that he thought about it, slightly out of character. Uncertain how else to respond, he shrugged.

She shrugged right back. "Well, he'll just be a few minutes." 

Not bloody likely. "Can I get you something to…" John paused: Sherlock would never be quite so hospitable.

"Tea would be lovely." She set a shopping bag on the table and then turned to lean back against it. "Is everything all right?" 

John went to fill the kettle, grateful for something else to do for a moment. "Yes, of course."

"You seem a bit… off." She smiled quizzically at him.

"Off?"

"Not your usual charming self."

He switched the kettle on and gave her his best impression of Sherlock's reptilian smile. "I can be incredibly charming when I want to be."

"Yes, but only when you're trying to get something you want." She gave him a knowing look.

"I meant it when I said I'm not done with John. He may have to stay another night."

"He's got work tomorrow."

"He'll call in."

"Oooh, don't tell me you're stumped! The great Sherlock Holmes, working all weekend to solve the mystery."

John tried to look slightly miffed. "It does happen."

"Maybe I can help. Three brains are better than two."

"Two and a half, including John." There, that sounded like something Sherlock would say.

She made a face. "Oh, don't start. He's actually quite clever, you know. In his own way."

John couldn't stop his eyebrows from shooting up at that. Fortunately, the kettle clicked off at that moment, and he had an excuse to turn away from her. He had to think of some way to get her out of here before he dug himself in any deeper. Either that or they just had to bite the bullet and tell her that they'd somehow, unbelievably, magically, switched bodies. 

That seemed like a bad idea all around, though: he hadn't yet been able to get Sherlock to discuss how and when they were going to tell anyone. They'd been a bit preoccupied with… other things. He felt a fresh wave of guilt.

And that opened a whole new can of worms, didn't it? She hadn't minded him running around with Sherlock in his free time, helping with cases and writing the blog. But if she knew the half of it, the sorts of dangerous things they so often got themselves into – not to mention what they'd got up to this morning – she wouldn't be terribly enthusiastic. 

"I brought him a change of clothes," she continued. "Considering that he didn't come prepared for a sleepover yesterday, I thought they might come in useful." 

"Good. I'm sure he'll—" 

He heard her footsteps behind him and realized she was walking to the bathroom. He turned around with her name on his lips, but she was already peeking through the slightly-open door. "Hello, love," she said, and then walked through and closed it firmly behind her. 

Oh, God. John walked a few steps toward the bathroom, his heart pounding in his chest. This would either be a complete disaster or it would be perfectly fine. It was all down to Sherlock, who generally was brilliant at improvising – though John wasn't, tended to react badly when surprised, and that definitely threw a spanner in the works. He walked halfway to the bathroom, then stopped, turned back, then walked nearly all the way there again. He heard muffled voices behind the door, but nothing overly dramatic. Nothing to indicate she'd caught him mid-wank, anyway. The voices grew quieter, and a moment later, the door opened and she stepped out. Her face was a bit flushed (humidity in the bathroom, most likely – God, hopefully not for any other reason) and she smiled.

"He's almost done. I'll just leave his things in here, if you don't mind?" She turned and walked into the bedroom, and John breathed a sigh of relief as she disappeared from view. Sherlock was even better than John gave him credit for.

The shower continued to run, inordinately loud in John's ears, and Mary didn't return. John blinked: something was wrong.

"Sherlock?" Mary's voice, from the bedroom, tense.

He walked down the corridor and stopped in the doorway. Mary stood at the foot of the bed, her shopping bag still in hand. She took a deep breath, pursed her lips, and then nodded, as if making up her mind. "John slept with you. Didn't he?"

John looked at the unmade bed and his heart sank. There was no point in denying it – it was completely obvious that two people had slept in that bed, and from the state of the sheets, that perhaps they'd done something more than sleep. 

"There was nowhere else for him to sleep." God, it sounded pathetic even to his own ears.

She made a sound of frustration and shook her head. "Don't lie to me, Sherlock. Don't you dare stand there and lie to me, not about this."

"I'm… Oh, God. It's not… okay, it is, but it's not entirely what you think."

"You have no idea what I'm thinking." Her voice was quiet, low. Dangerous.

"I don't."

"So tell me what it is. And know that I will ask John the same question the moment he comes through that door."

John forced himself to look at her. Her expression was carefully blank, as if she was waiting to see what he would say before deciding how to react. He had to tread carefully here. "It just happened, and it was a mistake. It won't happen again."

"Like hell it won't." Her lips curled into a grimace of sorts, a parody of her usual smile. "I know you're in love with him, Sherlock. And you're so careful, aren't you? I don't think he has a clue." She paused and took a steadying breath. "When you were dead, he loved the memory of you, and even though you hurt him, he still fell in love with you all over again these last few months. He thinks I don't know, that I don't notice, but how could I miss it?"

John closed his eyes, his head spinning. He wasn't in love with Sherlock. It wasn't like that at all. He cared for him, yes, had spent some time fantasizing about him, sure, and would even admit to being mildly obsessed with him – but that wasn't out of the range of ordinary for a close friendship. Was it?

She looked at the rumpled bedclothes again. "How long?"

"Sorry?" He opened his eyes again.

"How long have you two been sneaking around like this, having an affair behind my back?"

"We haven't been sneaking around. You know what we get up to."

"Right, of course. Solving cases, really? I'm not stupid."

"No! It's not like that, I swear. This was the first time."

"Even if I believed that, why would I possibly think you'd stop there, now that you've finally had each other after all these years?"

"Because he loves you." John struggled to keep the desperation from his voice. "And he needs you, so much. The two of you have a lifetime ahead of you, and—" 

"And yet, here we are." She dropped the shopping bag onto the bed and turned to look at him again. "You're having sex with my fiancé. What would you like me to say to that?"

"It was just a handjob." He winced even as the words left his mouth. God, he was being an arse, was making Sherlock look like an arse, even more so than usual.

"Oh, that's all? He gives great head, you know. You've got that to look forward to."

John cringed. "Mary…"

"And he fucks like a dream. Really, he can go for ages." Her expression was sharp, cold, something he'd never seen on her face before.

John took a deep breath. "I'm sorry, Mary. I am so, so sorry. I can be a selfish idiot sometimes, but you must know how much I—" He stopped himself just in time. The voice wasn't his own, even if the words were. He had to be mindful of that. "I am sorry. Please."

She watched him for a moment before crossing to stand right in front of him. "Believe it or not, I do understand." She paused, pressed her lips together, and her expression softened. "I wouldn't actually mind it, you know. If you two had been honest with me about it, it would have been fine."

John stared at her for a moment, certain he'd misunderstood. "Fine?"

She shrugged. "I know what the two of you mean to each other. And I know he's not completely mine. Not since you came back, anyway." She gave him an arch look. "I'm not opposed to sharing him with you on occasion. Hell, I already do in most ways. What's one more?"

John opened his mouth, but it was several seconds before the words organized themselves well enough to come out. "You can't seriously mean that if I'd rung you up this morning and said I'd like to give John a wank, you'd have said—"

"Wait 'til I get there so I can watch? We've talked about it before, John and I."

They had done, but in the middle of sex when they'd both had a bit much to drink, and he'd written it off as a teasing bit of fantasy. He hadn't thought she'd meant it. He shook his head, almost laughed, and carefully schooled it back down to confusion. "I don't…"

A small smile played at the corners of her mouth. "You can't be that naïve, Sherlock. Is it really so shocking?"

"Yes." John swallowed, retreated a bit. Sherlock: he was supposed to be Sherlock. "None of this is really my area."

"Oh, Sherlock." She took a step closer to him, watching his face intently. "It's only John, isn't it? There's never been anyone else."

He had no idea what to say to that. He could only stare back at her, overwhelmed by the idea that he might mean that much to Sherlock. That he did.

"I know how hard this is for you. I see the way you look at him." Her voice wavered a bit, and she reached up and cupped the palm of her hand against his cheek. "And you should see the way he looks at you, when you're not paying attention." 

There was a sound behind them and they both turned, took a step apart. Sherlock was standing in the doorway, towel wrapped around his waist. "Am I interrupting?"

Mary rounded on him, her expression suddenly dark. "Funny, I was about to ask you the same question." She looked pointedly at the bed, and Sherlock's eyes widened. John could actually see the moment when he worked out what had just happened. "Now it's your turn. He's already told me his side."

Sherlock closed his eyes briefly, and seemed almost to crumple where he stood. "It was my fault, Mary, completely my fault. I started it. He actually wasn't all that interested until I—"

" _John_!" John glared at him, and Sherlock went visibly pale. 

"No, Sherlock, I want to hear this." Mary crossed her arms over her chest. "Please, John. Do go on and tell me just how long you've wanted to shag Sherlock. You must have been thrilled to finally have a chance to make your move." 

Sherlock closed his eyes and sat heavily on the bed. "Shit, _shit_." 

"And let's not forget about the fact that he's completely in love with you, and you've just cruelly led him on."

John pressed a hand over his mouth at that, but Sherlock looked back up at her, defiant. "He's not a child. He knew exactly what he was getting into."

"How do you know? Have you asked him?"

Sherlock stared back at her, clearly uncertain how to proceed. 

"He's right," John said after a moment, and Mary turned to look at him. "He knows how I feel about him, and I knew it was just a one-off." 

Sherlock's expression was guarded, carefully blank. "I do know. How you feel, I mean. And I'm sorry that I…" He paused, swallowed. "That I put you in that position." He looked up at John, his eyes suddenly bright.

"You didn't." John took a shaky breath. "I knew exactly what I was doing. I wanted you. I have for a long time. I made a choice in that moment, and… I don't regret it."

"You…" Sherlock broke off and looked away, his expression one of barely concealed anguish. 

In a wrenching moment of clarity, John understood: Sherlock had been clinging to the idea that John didn't want this, that it was just something he'd done on impulse, that he'd regretted it. It had been the one thing keeping him afloat, and John had just ripped it away. 

There was no doubt that Sherlock loved him, that the things John had been feeling over the last twenty-four hours were part of a bigger picture John hadn't seen – or maybe hadn't wanted to see. And since Sherlock was in John's body, surely he'd felt John's love for Mary as well. And God, it must have _hurt_.

"How can I?" John shook his head and looked away, to where Mary was watching him through narrowed eyes. He felt utterly defeated, lost. In the space of a few minutes, he'd hurt the two people who meant the most to him in the world, and now it seemed likely that he was going to lose them both. 

"What do we do now?" Sherlock's voice so soft it was nearly inaudible. 

John wiped at his eyes. "No idea."

Mary inhaled so sharply that they both turned to look at her. She closed her eyes for a moment, and when she opened them again, she looked at John. "Why did you call him 'Sherlock'?"

John froze. "I didn't." Did he?

"You did, just now. Didn't he, Sherlock?"

She turned to Sherlock, who immediately said, "No, he—" He clenched his jaw and looked away. "Shit."

"That was far too easy." Mary turned to John with raised eyebrows. "Mind telling me what's going on, _love_?"

John stared at her, bewildered. "I don't... How?"

She turned to Sherlock, her eyes searching his face. "What did you do?"

Sherlock looked offended. "Why do you assume it was me?"

"It's always you, isn't it? Now tell me what happened, and don't leave anything out."

Sherlock's eyes narrowed as he stared back at her, and then a look of realization spread across his face. "Oh, God. How did I not see this before? You're a—" 

"Never mind that now." Mary's tone became anxious, and she leaned even closer to him, staring into his eyes. "Who did this?"

"No one did anything," Sherlock replied, still looking up at her with no small amount of fascination. "It was an accident."

"An accident? How could—" There was a flicker of fear across her face before she seemed to push it away. "When?"

"Yesterday morning."

"What happened?"

"We were working on a case, and it involved a matchbox with a glowing light inside. I didn't know what it did until it was too late."

Mary's brow furrowed and she stepped back again. "A body-switching curse. But a matchbox? That doesn't…" She gave him a sharp look. "Did you tell Mycroft?"

Sherlock grimaced. "Of course not. And I'd rather leave him out of it entirely, especially if you can—"

"I can't!" she spat. "Jesus, Sherlock, this is not something to be played at. You, of all people, should know better!"

John couldn't stand it any longer. "Would someone mind telling me what the fuck is going on?" 

Sherlock looked even more surprised. "And John doesn't know? This should be entertaining." He leaned back against the headboard of the bed.

Mary went pale and pressed her hands over her face. "Oh my God."

John glanced back and forth between the two of them, and something like nausea began to rise in his stomach. "What is it that I don't know?"

"This explains so much." Sherlock tilted his head, staring at her intently. 

Mary dropped her hands and gave him a pleading look. "Sherlock, please."

John huffed in exasperation. "Apparently we all have secrets today. Bloody fantastic."

"This is not how I'd planned this to happen," Mary said. She paused and took a deep breath. "Sherlock, I need a moment with John."

Sherlock scowled. "Fine. But I'm leaving the door open." The towel fell off as he stood, but he didn't bother retrieving it. John was momentarily distracted by the sight of his own bare arse flouncing through the doorway.

He turned back to Mary, who had been transfixed on it as well. "What the hell is going on? How did you know that we were switched?"

"You were talking about each other's feelings. Honestly, John, that ought to tip off anyone who knows the two of you."

"And you leapt from that to the idea that we'd switched bodies?" He shook his head, incredulous. 

"I promise I'll explain later, but first we've got to switch you back before it's too late."

"Too late?" A bizarre mix of hope and panic roiled in his chest. "Sherlock seems to think you can fix it." 

She looked slightly pained. "I can't, not any– I mean, I know where to find someone who can."

"How the hell do you know what to do in this situation?" He stared back at her in disbelief. "Why are you not freaking out about this?"

"Well, it's hardly the worst news I've had today, is it?" 

"No, it isn't. Oh, God." John cringed. "I don't suppose I can use the body switching thing as an excuse?" 

Her eyes narrowed. "For you and Sherlock getting it on behind my back? No. And I'm still pissed off about that, by the way."

John groaned. "He was jerking off in my body, right next to me."

"And you decided to help him out?"

"It's a horrible excuse, I know, but—"

"No, I get it." Sardonic didn't begin to describe her expression. "I also have a hard time resisting your cock."

"It's not exactly mine anymore, is it?"

Mary's expression changed completely, and she stood and tugged his hand. "We'll finish this conversation later. Right now, you need to show me this matchbox."

They went into the sitting room, where Sherlock was half under the sofa table, bare arse in the air. John felt a very clear jolt of arousal at the sight, and Mary elbowed him. He turned to look at her, mortified. 

"See how hot you are?" she whispered. "This is why I want to try the strap-on."

"Oh my God," John said, gaping at her.

"You can't deny you'd be up for it."

"We can plan the three-way later," Sherlock said, coming up again with handfuls of matchboxes. "Right now, we've got 219 of these."

John's brain stalled at _three-way_ , but Mary knelt on the floor beside Sherlock and picked up a matchbox. Her expression softened almost immediately.

"Of course! I haven't seen one of these in ages. Where'd you get them?"

"Client in France. His brother had opened one and gone mad. But he only sent the one. The rest of them just… appeared."

"Why the hell would you open something like this?" She shook her head in exasperation.

Sherlock looked properly chagrined. "I didn't know what it did. And once it was obvious, I assumed it would wear off soon enough."

"You thought it would—" John began, and then rolled his eyes ceiling-ward. Almost two days, and not a word suggesting he might know what was going on. 

Mary frowned. "It should have done. These aren't terribly powerful. And the replication isn't normal – at least, I don't think it is. It's probably malfunctioning. Not surprising, considering how old these are."

"But it's reversible, isn't it?" 

"Yes, should be. Though it definitely gets more complicated with every passing hour." She pulled her phone from her pocket and glanced at the time. "If I leave now, I might be able to find a solution by morning."

"On a Sunday evening?" Sherlock's eyebrows rose.

"Someone owes me a favor, and he works strange hours. Or he did, anyway." She stood and pocketed the matchbox, and held out a hand to Sherlock, who allowed himself to be pulled to his feet. 

John felt like a child again, listening to his parents discuss adult matters as if he wasn't present. He crossed his arms over his chest and glared at the two of them. "No one is leaving this room until I get some sort of explanation."

Mary and Sherlock exchanged a look. Sherlock held his hands up and took a step backward, clearly not volunteering to be part of this.

Mary turned back to John, wincing. "All right, fine. First, please know that I was planning to tell you this when the time was right."

"Tell me what?" One distinct possibility flooded his mind and the blood drained from his face. "Oh God, are you and Sherlock—"

"No, not that." 

Sherlock snorted in laughter, and they both snarled, "Shut up!"

Mary gestured to the sofa. "You should sit down." 

"No, I don't think so."

"No, I think you should."

"Just _tell_ me."

Mary pressed her lips together. "Right, so. There are quite a lot of things I haven't told you about my past, and my life before… you."

"What kind of things?"

She took a shaky breath. "God, where do I begin?"

"How about at the beginning? I'll tell you when I'm all caught up." He couldn't keep the anger out of his voice. 

"We really don't have time for this right now." She shook her head, clearly frustrated.

"How about just the important details, then? You said your parents died, that you had no other family or friends from your childhood. Was all of that a lie?"

She seemed to steel herself. "I told you they died in a car accident."

"Right."

"But they didn't. And I'm afraid I can't tell you more about how they died, just that they – and I, and many others – were involved in a…" She paused and seemed to search for the right words. "It was a complicated situation, involving—"

"Terrorists," Sherlock interjected from across the room. He was applying rosin to his violin bow, and seemed to find the conversation very entertaining. "Well, that's what Mycroft always said, anyway."

"You knew about this?" John glared at him, and then turned back to Mary. "You told him things about your past that you didn't tell me?" The idea that Sherlock knew and he didn't – not that it was so unusual, but _fuck_.

"I didn't tell Sherlock anything!"

"I'm just as surprised as you are," Sherlock added. "Though I should have worked it out sooner. Mycroft is really going to take the piss."

"And what does Mycroft have to do with— Oh, God. Does Mycroft know?" John choked out a laugh. How was this his life? 

"Of course Mycroft knows." Mary sighed, clearly frustrated. "I'm not allowed to tell you everything yet, not until we're married." 

"Oh, this sounds familiar! I have a tendency to be indiscreet, is that it?" He shot Sherlock a glare and Sherlock rolled his eyes.

Mary groaned. "Don't be ridiculous, John. You know there are laws about this sort of thing. You had a security clearance once; you ought to understand."

He felt himself spiraling out of control, anxiety ramping up again – but no, that wasn't coming from him. Was it? He took a deep breath and forced himself to calm down. "No, you're right, I know, I…" He paused as another possibility occurred to him. "Wait, were you MI6?" The thought was more than a bit exciting, he had to admit.

Mary opened her mouth and closed it again. "Not exactly. Not MI6, but… something like it."

John exhaled, feeling a rush of relief. This he understood; this was something that made sense. Sort of. Considering the circumstances, anyway. "And so this matchbox, it's, what, some sort of secret weapon? Spy stuff?"

Mary's expression was pained. "I wouldn't say weapon. More like a… joke."

John blinked at her. "A joke?"

"Yes, it's a joke. Supposed to be funny, you know. You switch bodies with someone for an hour, hey! How much fun is that?" She waggled her fingers in the air beside her face.

"None," John said, giving her an incredulous look. "It's not fun at all."

She shrugged. "It's a tiny bit fun."

"Have you ever tried it?"

Her smile was tight. "It's weird, I'll grant you. Though I'm sure a couple of days with no end in sight makes for less of a laugh."

John could only gape at her. "What the hell kind of spy were you?"

"One who dealt with very odd things. There's a whole Ministry for it, actually. Ah, shit – that's definitely above your pay grade."

"I think I need to sit down." John felt behind him for his chair.

"Yes, probably a good idea." She took a step backward, arms wrapped around herself. "And I should get going. It'll be tomorrow at the earliest, so you two should stay here."

"I think I should go home," John said, and they both turned to look at him. "I don't fancy sleeping on the sofa, and…" He shrugged. It probably wasn't a good idea to spend another night with Sherlock, considering. 

Mary frowned. "I'd rather the two of you stay together, in case I need to find you quickly." 

"She has a point." Sherlock sat sprawled in his own chair, still stroking the rosin up the bow, and still completely naked. _Jesus_.

Mary turned to John, who managed to drag his eyes away from the wanton display in the chair just in time to save a shred of dignity. She sighed. "We still need to talk about the rest of it, and there isn't time now. I have to… Oh, God. Both of you, come here."

John stood, and she took his hand, and Sherlock set his bow carefully on the shelf before coming to stand in front of them. She took Sherlock's hand and placed it in John's.

"This," she said, covering their hands with her own small fingers, "is just for tonight. Starting tomorrow, we're going to make some rules about how this is going to work in the long term."

John stared down at their joined hands – all three of them – and swallowed. 

Sherlock squeezed his hand, but his eyes were fixed on Mary. "You don't have to do this. I'll be fine, really."

"It's not just you, though, is it? Surely you've worked that out by now."

Sherlock hesitated for a moment, and then nodded. John squeezed his hand, unable to trust himself to say anything.

Sherlock's voice was full of raw emotion. "Are you certain?"

She squeezed their joined hands with her fingers before stepping back. "Absolutely. Now kiss him for me. Go on."

Sherlock turned to look at John, his eyebrows raised in question. John could only stare at him for a long moment. This was crazy, unexpected, and his head was spinning with the idea that he might not have to choose between them. It would have been an impossible choice, especially knowing he would have lost the other in the process. But now, this – he turned to look at Mary, who was smiling at him – this was everything. This was amazing. He didn't know what to say.

"Go on," she said. "Give me something to think about while I'm up all night doing research." 

John turned back to Sherlock and nodded. Sherlock stepped closer and reached up to slide one hand around the back of John's head, and John leaned forward, pressed his lips against Sherlock's. It ought to have been strange, kissing this face that was really his own, but it wasn't. It was Sherlock, underneath everything, and it was Sherlock kissing him back, sliding his tongue against John's, lips moving gently against his, scraping a bit where they both needed a shave. John smoothed one hand around his back, sliding over warm skin, and pulled him closer.

"Oh, that's lovely," Mary said, and they both turned to look at her. Her cheeks were flushed and her eyes dark, and she bit her lip. "You have no idea how much I want to stay and just watch."

"Sure you can't?" John asked, and held out his hand. 

She looked at it for a full second, and then took a step back. "I think I'll wait until the two of you are sorted. It's been weird enough already." She looked as if she wanted to say something more, but instead she smiled and wrapped her scarf around her neck and headed for the stairs. She turned back just before disappearing through the door. "I'll be by in the morning. I'll expect breakfast. And sordid details."

John stared at the doorway for a long moment after she was gone, so lost in his own thoughts that he didn't even hear the street door open and close below. He finally turned to look at Sherlock, who was still standing less than a foot away, and naked as the day he – or John, anyway – was born. 

Sherlock, who loved him more than John had ever realized, who may never have loved anyone as much as he loved John. Who had literally and figuratively worked his way into John's very skin, and who had done his best to hide every flicker of feeling these last few months, simply because he knew that John loved Mary – and only Mary, he'd thought. He had been prepared to sacrifice his own love so John could have his, and he would never have said a word about it. John swallowed, but didn't let himself look away. 

Sherlock stared back at him through wide eyes and watched the train of thoughts that must be so plainly written on his face. John looked down at their still-joined hands and smiled.

*****


	5. Five

Sherlock squeezed John's fingers and let go. He took a step backward, one hand rubbing at the back of his neck. "So." 

"So." 

"That was big."

"It was." John swallowed down a sudden flare of anxiety. "Are you all right?" 

"Yes, of course. But I didn't just experience a shift in my perception of reality."

"Well, I wouldn't go that far. I mean, I've known how I felt about you for a long time. I just never thought you'd be interested. I suppose Mary being okay with it was a bit of a surprise, but not— What?"

Sherlock was staring at him with the sort of expression he usually reserved for people he thought were complete idiots; it was disconcerting to see it so clearly on his own face. Sherlock immediately schooled his features into something more unreadable and looked away. "Right, of course. Tea? I'd like some tea."

"Oh, you… You mean the other stuff." 

"Yyyes." Sherlock's eyes narrowed, and he looked as if he were completely uncertain how to proceed. "So…"

"She's never said much about her past, so I suppose it should have been obvious there was something there. But I understand. It's not as if I've told her everything I did in Afghanistan."

"Right." Sherlock looked terrified for a split second, and then wiped his expression clear once again. He gave John a tight smile. "I think I'll get dressed."

"Now? But—"

"Your penis is far less impressive when the room is this cold." 

"Everyone's penis is less impressive when the room is cold."

"And you've got a lot of experience with that, have you?" Sherlock walked past him, on the way to the bedroom.

"I was in the army."

"Just how cold does it get in Afghanistan?"

"Cold enough." John stared after him for a moment. Was he was meant to follow? No, Sherlock wouldn't be that coy. 

He exhaled and turned toward the kitchen. "I'll put the kettle on. Again." God, how many times had he attempted to make tea today?

He filled the kettle, thoughts swirling. He wasn't entirely sure what to make of Sherlock's withdrawal just now. Several possibilities sprang into his mind, each more dire than the last. No, the first was most likely: he was probably giving John space to sort out what had just happened with Mary. John clenched his jaw at that – surely he ought to be more upset about it all, more freaked out, more _something_ , but he wasn't. Strangely enough, he felt like he knew where he stood with Mary at the moment – or at least, he knew well enough to be getting on with. But this, with Sherlock, was entirely new. He'd spent most of the day not-thinking about it, pushing it out of his thoughts. Perhaps Sherlock had done as well, and now they both had to face it.

Pity it wasn't as simple as diving into the sheets for a mindless shag. Apparently not, anyway.

Sherlock emerged a few minutes later, dressed in the clothes Mary had brought, and settled at the table with his laptop. John brought two mugs of tea to the table and sat across from him, but Sherlock didn't look up.

John tried very hard not to fidget. "So if this body switching thing is reversible, we should be able to help your client in France."

"Perhaps." Sherlock took a sip of tea. "I'll email Mr. Thibaud's brother and let him know we may have a breakthrough."

John was quiet for another moment while Sherlock tapped at the keyboard. "Do you have any idea how Mary is going to be able to switch us back?"

"None, truthfully. It's not my area of expertise."

"She implied it was Mycroft's, though."

Sherlock made a face. "Everything is Mycroft's area of expertise." 

"Just… please tell me you didn't refuse to ask for his help because of your fucked-up sibling rivalry."

"If you'd prefer that I lie to you, I'm happy to oblige."

John leaned his forehead against the table. "You are such an arsehole. We could have avoided all of this, you know."

"All of it?" There was a strange note in Sherlock's voice, and John looked up again. Sherlock was watching him over the top of the laptop now, his expression wary.

John sighed. Without this bizarre situation, they wouldn't have realized their feelings for each other. Neither of them would have had the nerve to act on it, and Mary wouldn't have stepped in and offered… What exactly was she offering? That John would shuffle back and forth between them, like a child in a shared custody arrangement? Would Mary and Sherlock pair off on occasion, leaving him on his own? Or would all three of them have sex together? His mind filled with a series of images, each more explicit than the last, and he bit his lip. 

"What?" Sherlock asked.

"Just… thinking."

"Obviously." 

"I was thinking that you're right. I'm glad this happened, and I wouldn't change a thing."

Sherlock gave him a long look. "That's not what it looked like you were thinking."

"What did it look like, then?"

"Sure you aren't having second thoughts?" 

John's breath caught. "No. Are you?"

"No." Sherlock looked back at the screen of his laptop. "But if you were, it would be understandable."

"I'm not. Definitely not." John watched him for a moment. Was he uncertain that John really wanted this, or was it something else? Getting a read on Sherlock was nearly impossible under normal circumstances, and this extra layer of complication didn't help. Silence stretched out between them for half a minute, and John decided action was best. He set his mug of tea on the table. "I need a shave and a shower."

Sherlock nodded, but didn't look up. "Thibaud's ex just messaged me. This should be interesting." 

John hesitated. He wanted to ask Sherlock to join him, to reassure him and – well, tick a fantasy off of the list. But perhaps moving slowly was best. Wrapping up the case would settle Sherlock's mind, and then there wouldn't be anything to distract them. He felt a twinge of excitement at the thought.

"Yeah," he said, and stood. 

He shaved carefully, and that was an experience, Jesus. He'd never appreciated just how angular Sherlock's face was until he had to drag a sharp blade over it. He managed well enough, though it wasn't as good a job as he'd like. Once in the shower, he mostly avoided the temptation to explore Sherlock's body. Now that he knew the situation was temporary, it seemed like a violation of Sherlock's privacy to do anything more than clean the important bits.

Choosing something to wear from Sherlock's vast assortment of expensive clothes was an adventure in itself. And everything was tailored, for fuck's sake; if Sherlock gained even a pound, he'd have to go shopping. John looked forward to being back in his own body for the comfort of his wardrobe alone. 

Sherlock was sitting cross-legged on the sofa when John returned, laptop balanced on his knees. John glanced over at him and then did a double-take.

"What are you wearing?"

Sherlock looked up at him. "Sorry?"

"On your face."

"Reading glasses."

John groaned. "I do not have a vision problem."

"So you keep insisting, but it's making a fair bit of difference. You'll see soon enough."

John vanished into the kitchen, grumbling, and retrieved the bottle of wine they'd bought the day before. God, it seemed like a week ago now. "Wine?" 

"Absolutely."

He fished in a drawer for the corkscrew. "So did you happen to have a pair of reading glasses just lying about?"

"No, I bought them."

John twisted the corkscrew into the cork and levered it out with a satisfying pop, then carried the open bottle and two glasses over to the sofa table. "I am actually going to miss a few things about being in your body."

"Oh?" Sherlock continued tapping at the keyboard.

"I've enjoyed being taller, for one thing. And having such big hands is rather useful."

Sherlock looked up at him with a small smile, and John was struck by how adorable he looked with glasses on. No: how adorable John himself looked. Jesus, this was going to be quite a readjustment, wasn't it? 

"So did you buy reading glasses for a case?" He poured two glasses of wine and handed one over to Sherlock.

"No, I bought them just now. I went down to the shop on the corner while you were in the shower."

"You went out just for that? My vision must be a lot worse than I thought."

"No, I went for…" Sherlock paused and took a sip of wine, and his cheeks tinted slightly. "Other things."

"Oh," John said, and then raised his glass to his lips. Realization sunk in, and he looked up again. "Oh. You mean…"

"Yes." 

"Right." So apparently Sherlock wasn't feeling as uncertain as John had thought. He chewed his lower lip – Jesus, the implications. Several sexual scenarios played out in his head at once, multiple variations on a theme. He took a sip of wine. They should talk about this first, sexual histories and testing and such. He cleared his throat. "You know, we don't have to do anything…" Jesus, he was a doctor. Why could he suddenly not talk about sex without waffling like a teenager? "…you're uncomfortable with."

"There's not much I'd be uncomfortable with, when it comes to you." The words had spilled out quickly, and Sherlock looked taken aback for a moment, as if he hadn't meant to say them aloud. "Are you uncomfortable with… anything in particular?"

"No." He'd answered without thinking it through, but it felt true. He wanted anything, everything, from romantic cuddles to the completely filthy stuff he generally associated with porn. Was that coming from him, or was it what Sherlock wanted? He wasn't sure at the moment. John wet his lips. "Though it's going to be strange to be in each other's bodies. Is there anything I should know about… you?"

"Like what?"

"History, I suppose? You've been tested, right?"

Sherlock swirled his wine and stared into his glass. "Mycroft makes sure of it."

Ah, of course. John nodded and looked down at his hands. Sherlock's hands, actually. "Mary and I were both tested about a year ago, when we first started dating, and we've only been with each other since."

Sherlock was quiet for a few seconds. "It's been a while. Years."

John looked up at him, and was startled for a moment by how young he looked. "Really? I wasn't sure you…"

"Until I met you, I didn't think I ever would again."

John was momentarily struck speechless. He finally nodded and looked away, toward the kitchen. First things first. "Are you hungry?"

Sherlock's pupils shifted to the side as if he was thinking about it. "Yes, I suppose so. Getting there."

"I'm going to cook something." 

"We've eaten twice today. Is a third time really necessary?"

John picked up his wine glass and stood. "Trust me; you're going to need your strength." He looked back once he reached the kitchen to see Sherlock grinning at the screen of the laptop.

*****

"It's frustrating to hit so many dead ends." Sherlock stroked the stem of his wine glass in a way that was slowly, but surely, driving John mad.

"So she isn't a suspect?" 

"I'm sure she wasn't involved. She's now broken off her affair with the actor as well – said she felt responsible for Thibaud's breakdown."

"And that's not suspicious?"

"She knew nothing about the matchboxes, as far as I could tell."

"How do you get all of that from a written conversation?"

Sherlock smiled, and John felt his stomach do a little tumble. Oh, Jesus, _tumble_. 

"It's what I do, John. Though it would have been much easier via Skype."

"But not while you look and sound like me." 

"Right." Sherlock picked up his empty wine glass and frowned into it. "Should we open another bottle?"

"I don't think so. I'm feeling that far more than I expected to."

"Yeah, I don't drink very often." Sherlock set the glass aside and shifted slightly in his seat. He took a deep breath and looked up at John, and there was unmistakable heat in his eyes. "So shall we…?"

"Clean up? Yes, good idea."

There was a beat and then Sherlock laughed, and John felt his heart pounding in his throat. It had been like torture to sit across the table from him for the last hour, an arm's length away, but yet he felt a strange desire to prolong the tension as much as possible. Not much longer, though. He stood and collected the dishes from the table.

To his great surprise, Sherlock volunteered to wash up. Once the table was cleared, John leaned back against it and watched him, watched the way he moved in John's body with an economy that was so unlike his normal demeanor. In just two days, they'd become surprisingly accustomed to being in each other's skin. 

At the same time, it was strange to look at his own body and feel such desire for it. He'd been pushing that desire to the edges of his thoughts all day, but now he let it back in, let it fill him. This was how Sherlock saw him, how Sherlock felt when he looked at John. He let his gaze drift, roaming over his own body, to the small of his back (want to lick right there) and the nape of his neck (brush my nose there, inhale), and down to his arse ( _oh God _). Just a few more minutes and they'd have everything else out of the way, and then they had all night.__

__God, where to begin? Anything, everything – he knew exactly how to make that body writhe with pleasure. He knew where to touch, where to lick, how far he could push. Sherlock didn't know, couldn't know all of it, and the idea of showing him exactly how John wanted Sherlock to touch and tease him when they were switched back again – it was heady._ _

__John waited until the last dish was rinsed before succumbing to temptation and pressing his lips against the nape of Sherlock's neck._ _

__"Oh, God." Sherlock's head fell forward and he braced both hands on the edge of the sink. "I've always wanted to do that. How did you know?"_ _

__"I've been wanting to do it for two days now," John whispered, and then trailed the tip of his tongue up to the hairline. "Coincidentally, it's a very sensitive spot on my body."_ _

__"So it is. Ah, Christ."_ _

__"And so is this one." John pressed his lips against the skin behind Sherlock's ear and slid his hands up inside Sherlock's shirt._ _

__Sherlock's head fell back against John's shoulder. "This is fascinating."_ _

__John smiled against his skin. "Oh, is it a case now?"_ _

__"Of sorts, yes. So much conflicting data, new responses to catalog. It's like I've been rewired."_ _

__"Here's more data, then," John whispered, and sucked one earlobe._ _

__Sherlock made a soft sound, and it was as much innocent wonder as it was raw desire. John slid his arms around him and squeezed, momentarily overwhelmed. Had Sherlock ever done this before? He'd had sex, obviously, but had he ever stood in a kitchen after dinner, in the arms of someone who wanted to make love to him?_ _

__"Don't stop," Sherlock whispered, and his hands closed over John's on his stomach._ _

__"No chance of that happening." John teased the shell of his ear with the tip of his tongue, and Sherlock turned in place and kissed him._ _

__He hadn't expected Sherlock to be so very good at kissing; to the extent he'd given it much thought, he'd expected it to be a bit sloppy and overly enthusiastic. But instead, Sherlock took his time and moved slowly, lips moving against John's, slight pressure, teasing with just the tip of his tongue before sucking on John's lower lip. He felt like he was floating, and God, what was happening? Was it that Sherlock wasn't used to being kissed this way, and that was what he was feeling?_ _

__Sherlock pushed him backwards until he bumped into the table they'd just cleared, and started unbuttoning the shirt John wore._ _

__"Here?" John asked, and then gasped when Sherlock flicked his tongue across an exposed nipple._ _

__"I have a fantasy involving this table."_ _

__"Oh, fuck," John hissed, and braced against the table. His own nipples were not this sensitive, and Jesus, that was amazing. Sherlock sucked lightly and then John was rock hard, and Sherlock hadn't so much as brushed against his cock. "What else happens in this fantasy?"_ _

__"I'm getting to it." Sherlock pushed the shirt off of John's shoulder and moved to the other nipple. He worked it with his tongue while he pinched the first one lightly between his fingers, and John nearly whimpered. How could that feel as amazing as it did? And why weren't his own nipples directly wired to his balls, because _damn_ , he'd been missing out._ _

__"Jesus, you could probably come like this," John said, and clenched the table even harder._ _

__"I have done, once," Sherlock whispered, and planted wet kisses down his abdomen. "With no other stimulation."_ _

__"Adding that to the list of things I want to do to you."_ _

__Sherlock groaned, mouth pressed against John's belly. "God, I'm so hard it hurts. Is that normal for you?"_ _

__John grinned, but before he could answer, Sherlock pressed the tip of his tongue into John's navel, and oh, God. He hated having his navel touched generally. _Hated_ it. But this – it was incredibly erotic, like he was being licked on the inside, tendrils of pleasure going right to his cock. "You're right; this _is_ fascinating. It feels so fucking different." _ _

__"I wonder if this will?" Sherlock dropped to his knees in one smooth movement, and looked up at him with a sly smile._ _

__"Oh, God," John breathed. He watched as his own familiar fingers unfastened the button of his trousers, drew down the zip, and tugged the fabric down just enough to free his cock. Sherlock's gaze dropped to the erection hanging in front of him and John felt a strange stab of jealousy: it was somehow unfair that one of his fantasies was about to come true and he was on the other side of it._ _

__Sherlock pressed his lips against the base of his cock and closed his eyes, paused to inhale before planting a line of soft kisses up the underside. He licked them away with soft swipes of his tongue, leaving little patches of wet skin down the underside of the shaft, just enough wetness to hint at what was coming, enough to make John strain his hips forward a fraction of an inch, silently begging. It was light and teasing, excruciating, beautiful, and God, he never wanted it to stop. Sherlock paused and his eyelids fluttered shut for a moment, as if he was barely holding himself back. He exhaled against the glans, warm, damp breath that made John shiver, and then looked up at John._ _

__"Going mad yet?" He licked a bead of fluid from the slit._ _

__John nodded and twined his fingers in Sherlock's (his, fuck) hair. "Don't you dare stop."_ _

__Sherlock pressed an open-mouthed kiss against the underside of the glans, wriggling the flat of his tongue and sucking lightly, and there, it was so close, so close to being in his mouth. John stared down at him, at where Sherlock's eyes were practically daring him to do something. Was this what Sherlock fantasized about? About John himself on his knees, mouth ready to be fucked? He finally couldn't bear it any longer, couldn't stop himself from pressing lightly at the back of Sherlock's head._ _

__"If you want it," Sherlock said, lips moving against the sensitive skin, and John pushed forward, held his (own) head still and pressed his (Sherlock's) cock into his mouth, and _oh God_ that was exactly what he needed. He pulled out until Sherlock's lips ringed the crown and then pushed in again, farther this time. Sherlock's eyes widened, and John exhaled, shakily._ _

__"You can take it," he said, his voice little more than a hoarse whisper. "Just relax, and trust me." He smoothed his thumbs over Sherlock's temples and shifted his hips back. "Breathe."_ _

__Sherlock inhaled and then John pushed forward until Sherlock's nose was pressed against hair and skin. It had been a while since he'd done this, but he hoped his body would remember. Sherlock's hands went to John's hips as he pulled back again._ _

__"All right?" John asked._ _

__Sherlock pulled off, face flushed, and looked up at him. "I didn't know you could do that."_ _

__"Most people don't."_ _

__"Adding that one to my list. Show me again."_ _

___Jesus._ John's mouth opened and closed again. "Right, so breathe on the way down, and try to relax and just—"_ _

__Before John could finish, Sherlock's mouth descended on him again, this time with confident ease, and he felt the head of his cock touch the back of Sherlock's throat. Sherlock swallowed around him then, and John groaned. It took a few more tries before Sherlock coordinated the breathing with the movement, and of course he'd be a quick study, wouldn't he? And God, it was amazing – no one had ever done this for John, and now he understood exactly why his handful of fuck-buddies had liked it so much. It was an incredible sensation, tight and hot, more like intercourse than oral sex, and he found himself getting too close too quickly._ _

__"Stop, stop," he said, and pushed at Sherlock's head. "I don't want to come yet."_ _

__Sherlock pulled off and nuzzled the base of his cock. "You'll be able to come again in half an hour." His voice was a bit hoarse, and oh, it was _hot_. _ _

__"Ah, fuck. I'd better be."_ _

__It didn't take long after that: Sherlock's mouth was hot and his tongue was exquisite and his hand stroked in counterpoint, and John's knees nearly buckled when he came._ _

__Sherlock pressed his forehead against John's hip and panted. "I've wanted to suck you off in the kitchen for ages. You've no idea."_ _

__"For the record, you can do that anytime." John stroked the top of Sherlock's head and closed his eyes, his brain still buzzing with endorphins. "Any other fantasies we can take care of here in the kitchen?"_ _

__"Far too many for one night."_ _

__Sherlock stood and kissed him, mouth still sticky, and John's mind reeled at the taste of semen that wasn't quite his own. John pulled him closer, only barely fighting the impulse to lick his mouth clean, and felt a hard cock pressing against his thigh. He reached down and stroked his fingers up the length of it, and Sherlock whimpered into his mouth._ _

__John turned his head out of the kiss and pressed his forehead against Sherlock's. "How about the bedroom, then?"_ _

__Sherlock smiled up at him. "Even more in there."_ _

__"We have to start somewhere."_ _

__Sherlock kissed him again, a soft, sweet kiss that promised so much more, and John couldn't resist unfastening the jeans he wore and sliding a hand inside. The moment his fingers touched soft-hot skin, Sherlock melted against him._ _

__"Oh, God," Sherlock breathed, and pressed his forehead against John's shoulder. He reached down and stilled John's hand. "I want to do this in a bed."_ _

__John let his lips brush Sherlock's ear. "I think you really want to bend me over this table."_ _

__"Fuck, yes. But not tonight." He looked up and his expression was startling, almost desperate. "Please."_ _

__John felt something twist in his chest: he couldn't remember the last time he'd seen a look like that directed at him, so full of longing and raw arousal. He wondered what Sherlock saw, looking back at him right now._ _

__"Go on, then." He withdrew his hand and tugged his trousers up enough to walk, and followed Sherlock down the corridor to the bedroom._ _

__They undressed each other in semi-darkness, planting kisses on exposed skin and taking their time. John lingered over the scar on his shoulder for a long moment – he hadn't thought much of it in ages, but seeing it on another body like this was strange. And of course, Sherlock had scars of his own now, scars John had been reluctant to ask about. John suspected the scars weren't limited to his skin, that there was quite a lot more for them to discuss. But later: this, now, was much more important._ _

__They stood and kissed for a long minute, hands roaming over warm skin, breathing the same air, and John was sure he'd never experienced anything like it. Though he had – he knew he had, remembered frantic nights of not being able to touch his lover enough, of lingering in bed all the next day and making love for hours, ignoring the rest of the world. Perhaps it was Sherlock who hadn't felt this before._ _

__He pulled Sherlock with him toward the bed and they toppled onto it, mouths still locked on each other's skin. The weight of a male body on top of him was new, and John spent a few seconds cataloguing the sensations: his thighs pushed apart by a knee, a hard cock pressed against his thigh, long lines where there were usually soft curves, and body hair brushing his skin in places he didn't usually feel it. And even more fascinating was that it was _his_ body, and so despite this newness, he knew what to do, how to be. It didn't have to be slow and gentle, careful, as one might tentatively explore a new lover's body. It could be something else altogether, anything. _ _

__"What do you want?" He exhaled against flushed skin, fingers stroking the back of Sherlock's neck._ _

__Sherlock made a soft sound of pleasure at that touch. He pressed John's thighs further apart and slid his erection along the crease between thigh and groin, and dipped his head down to kiss John softly. "I want to fuck you."_ _

__"Yes," John said, and then there was a beat where his brain caught up with his body. "So I haven't… not this way." This probably wasn't the best time to admit that the entirety of his sexual experience with men had been in the form of hand jobs and blow jobs. It was rather unexpected to be the inexperienced one here._ _

__"But I have." Sherlock planted small kisses along his jawline. "And I… well, my body, anyway, is accustomed to anal penetration."_ _

__"And that means… what, exactly?"_ _

__"Fingers, mostly. In the shower." He nuzzled at the joint of neck and shoulder, and John shivered, both from the sensation and the mental image of Sherlock in the shower, fucking himself with his fingers, water streaming down his body._ _

__"Just fingers?"_ _

__Sherlock chuckled and slid down the bed a bit, breath ghosting over one nipple, _oh God_. "No."_ _

__His tongue flicked against sensitized skin, and John groaned, slid a hand around the back of Sherlock's head, his fingers carding through his own short hair. Under normal circumstances, he would have felt anxiety at the very idea of being penetrated in that way, but right now all he could think about was how much he wanted it. He had no idea if that was coming from him or from Sherlock, but at the moment, it didn't matter._ _

__"So how do you want me?"_ _

__Sherlock moved to the side and propped his head up on his hand, and stared at him with dark eyes. "Turn over."_ _

__John leaned over and kissed him again before turning onto his stomach. Sherlock straddled him—literally getting a leg over, John couldn't help but think—and slid warm hands up his back and over his shoulders._ _

__"You're going to like this," Sherlock whispered, and then trailed kisses down John's back, moving down his body as he did. John felt his cock, hot and heavy, against his thighs and calves. Sherlock bit his arse lightly and John yelped, wriggling. "Sorry. I know I'm ticklish there, but I couldn't resist. Tuck your knees under."_ _

__Almost immediately, the position made him feel incredibly exposed. John had a flash of anxiety then, the conflict between his own mind and this body thrown into sharp relief._ _

__Sherlock settled behind him and drew the tip of his tongue down John's spine, leaving a trail of sensitized skin in his wake. John expected him to stop when he reached the cleft of his buttocks, but he didn't. John felt his hands pushing, prying his flesh apart, and _oh God_ , was this going where he thought it was going?_ _

__Sherlock shifted on the mattress behind him. There was warm damp breath against his skin, and then the feathery tickle of the tip of Sherlock's tongue working its way down, down, and John was immensely glad he'd been thorough when he'd showered. The tongue marked a wide circle around his anus, light and wet and _fuck_ , everywhere except where he suddenly, desperately wanted it. He buried his face in his arms and groaned in frustration, and after an excruciatingly slow spiral inward, Sherlock finally flicked his tongue lightly across the center of his anus._ _

__"God, that's… _God_." John shifted his hips back slightly, wantonly, and was amazed that he wasn't blushing. In his own body, he'd be mortified, but right now he just wanted more._ _

__Sherlock chuckled softly and blew across the wet skin, making John shiver. He began circling his tongue again, this time with more pressure. The sensation of that soft tongue lapping at his anus was incredible, filthy, and John clenched the duvet in his fists. He'd done this to girlfriends before, but no one had done it to him, and _Jesus_ , why hadn't he asked for it? _ _

__Not that it mattered now, because here they were, and when Sherlock pressed the tip of his tongue firmly into the center, John exhaled a stream of filthy words. The tip of his tongue pressed in again, and again, a millimeter deeper every time, and God, he was being fucked by a tongue and it was perfect, amazing, and not nearly enough. It was all he could do to stay still and not writhe against Sherlock's face. He felt lips press against his skin as that tongue slowly moved in and out, and then Sherlock's fingers slid underneath him, wrapped around his aching cock and stroked in time with the thrusts of his tongue._ _

__"Fuck, you're going to kill me," John groaned. "Oh, God."_ _

__A moment later, Sherlock's mouth disappeared and John whimpered. The mattress shifted and there was a rustling sound, and then a cool, slick finger pressed into him._ _

__"Oh God, yes," he said, and grinned into the duvet. Just a few minutes ago he'd been nervous, and now he was practically begging for it. That finger twisted and slid out, and _oh_ , that was incredible. Then there was more lube and more pressure – two fingers, carefully pressing in, the thumb massaging the skin just below his anus, and then the fingertips curved down a bit._ _

__He moaned at the sensation, pleasure centers lighting up left and right. It was ironic that he'd spent so much time checking patients' prostate glands at the clinic, but hadn't really explored his own in a sexual way. He'd clearly been missing out, and oh, Sherlock definitely knew what he was doing. Was this how he fingered himself? It was, of course it was: he was showing John how he liked to be touched, licked, fingered, fucked, and next time it would be John doing this, all of this. He tried to focus enough to catalog it: very light pressure, slight circular motion, with the thumb pressing up from the outside, and _fuck_ , where had this been all his life? It was incredible, perfect, but still not enough. He needed more pressure, harder, faster, maybe—_ _

__"Fuck me," he whispered, "now, now."_ _

__"Yes," Sherlock said, and all John could hear was the sound of his own voice, husky with arousal. The fingers slid out again, and there was another moment of shuffling on the bed. John breathed through the sounds of Sherlock tearing open a foil packet and rolling on a condom, and he startled a bit at the cold slick of more lube being smeared against his skin. The first press of cock against his anus was strangely tense, but the head pushed in, and then it was the weirdly erotic sensation of his rectum being stretched open and full. It was tight, on the verge of too much, but _good_._ _

__"Oh God, you feel fantastic." Sherlock's voice shook, and he smoothed a hand over John's back, otherwise completely still. Just as John began to get impatient, he pulled out an inch, enough that the glorious slide of skin made John catch his breath. He knew – in theory, anyway – that the rectum was sensitive, but it still surprised him that this felt good at all._ _

__"All right?"_ _

__"Yes, yes, God." He'd never done this, had never even thought seriously about it, Mary's occasional hints about pegging aside._ _

__Sherlock moved with long, slow strokes at first, careful, deliberate, and John felt his body accommodate the stretch, relax around it. It was bizarre, amazing, walking a fine line between discomfort and pleasure, and he pushed back against Sherlock, not exactly certain what he was asking for._ _

__"Can you—"_ _

__Sherlock shifted then, changed the angle, and oh, there, _fuck, there_ – that was why people did this, right there, and it suddenly wasn't enough. _ _

__"More, come on."_ _

__"Yes, just let me—" and Sherlock shifted a bit, braced himself with one hand on the mattress, and started fucking him in earnest._ _

__John shifted his hips, trying to keep the angle right, and oh, God, this was glorious. He moved forward, nearly dislodging Sherlock in the process, and gripped the headboard. There, more leverage like that, and he could push back to meet Sherlock on every thrust. It still wasn't enough._ _

__"Harder, fuck, can you…?"_ _

__"Wait, stop." Sherlock pulled out and pulled John's shoulder, and John rolled onto his back. Sherlock looked down at him and took a shaky breath. "Like this. I want to see you."_ _

__John stared up at him, and with a jolt remembered that this wasn't Sherlock's face. It was his own, and this was what he would look like making love to Sherlock. When Sherlock pushed back in, John watched the way his jaw went slack and his eyes fell closed, and John looked up to the ceiling, uncertain for a moment that he could handle seeing this, watching his own face this way._ _

__But of course, Sherlock was seeing the same thing, wasn't he?_ _

__"Kiss me," John said, and Sherlock leaned forward, pressing John's thighs into his chest – apparently Sherlock was more flexible than John had realized – and kissed him. He shifted his hips then, pulled out and pushed in, and John's cock was caught between their bodies._ _

__And oh, yes, he would definitely be able to come again, and fairly soon. He reached between them to squeeze his cock, and Sherlock leaned down to whisper in his ear, "You feel so fucking good."_ _

__"Oh God, so do you. I had no idea." Sherlock was still moving slowly, torturously so, and John tried to shift his hips down to meet his thrusts._ _

__"Had no idea of what?"_ _

__"How much you like being fucked." John gritted his teeth and pushed at his shoulders. "So get to it, will you?"_ _

__Sherlock chuckled at that, and John wondered if he'd overheard Mary's comment about John's ability to last. He'd find out soon enough, anyway._ _

__"Hold on," Sherlock said, and John reached a hand behind him to brace on the headboard, and Sherlock began to fuck him – _hard_._ _

__John shifted his hips, trying to find the right – _yes-there-fuck_ – and it was amazing: indirect pressure on his prostate, friction, skin and warmth, but what nearly overwhelmed him was the unexpected sense of intimacy, of having another person inside him. He stroked his cock, erratically at first, and then faster, and he could feel his orgasm building, pressing in, intense, white-hot. The sensation of a cock in his arse somehow intensified everything, far beyond his usual experiences with sex, and he cried out, unable to stop himself, coming all over his hand, _fuck, fuck_. Sherlock stopped moving and held him through it, breathing hard, and leaned down to kiss his forehead as John collapsed back against the mattress._ _

__He was shaking. Fucking _shaking_. He closed his eyes and floated on a sea of endorphins, total orgasm high. "Jesus Christ."_ _

__"I prefer Sherlock, actually."_ _

__The smirk was audible, but John didn't even have the energy to fire back. "That was fucking amazing."_ _

__Sherlock slid nearly all the way out, and John felt a strange throbbing in his rectum. "Is it all right if I finish?"_ _

__"Yeah, 'course."_ _

__Sherlock started moving again, more slowly this time, deliberately, and John stroked hands up his sides, desperate to touch him, to do something besides lie there. He was ridiculously blissed out and emotional, and he had to bite back the horribly sappy words floating around in his head. If he still felt them in a month, when they'd done this a lot, in their own bodies, then he'd say them. Maybe not in the middle of sex. Maybe over dinner, with Mary there, just so everyone was on the same page._ _

__Sherlock was close now; he could see it in the way his arms shook and the way his jaw clenched, the way his eyes were nearly black._ _

__There was something else John liked, something Sherlock wouldn't know about. He reached up and pulled Sherlock down, and kissed him, then pressed lips against his ear._ _

__"Oh, God, just like that… Fuck me, yes… Want to see you come, want to feel it… You feel so good… God, I want your cock in me forever, never stop…"_ _

__Sherlock exhaled, almost moaned, and pressed his forehead against John's shoulder. "Oh, God."_ _

__"I can't wait to fuck you like this, when I'm back in my own body. Gonna fuck you for an hour. And I want you to fuck me too. No one's ever done that, but I want you to. I want you to fuck me while I'm inside Mary, and I want to fuck you while she watches." The words spilled out now, and he wasn't quite sure where they were coming from, but God, yes – they were true. "I want to teach you how to eat her pussy, and I want to fuck her while you do it. I want to blindfold you and see if you can tell the difference between our mouths. I want the two of you to make me your slave for a night, make me do every dirty thing you can think of. I want—"_ _

__"Ah, fuck," Sherlock breathed, and his thrusts became erratic until he pushed all the way in and cried out, teeth digging into John's shoulder._ _

__John wrapped his arms around him and held him, feeling his body rise and fall with his panting breaths, and pressed dry lips against his temple._ _

__"Oh, God. You… That was…" Sherlock voice trembled a bit, as if he might be on the verge of losing control of his emotions._ _

__John poked him firmly in the ribs. "The best fuck of your life?"_ _

__Sherlock made a sound almost like a laugh, and then John felt him swallow, exhale. "Unexpected, I was going to say. But… yes."_ _

__Warmth spread through John's chest, and he tightened the embrace. "I let you do all the work. I'm not usually that passive in bed, I promise."_ _

__"You'll have to convince me of that." Sherlock snuggled against his shoulder, warm breath brushing against John's chest. "In the morning."_ _

__"Maybe around midnight, if you're up for it."_ _

__"Will I be? You're the expert."_ _

__John frowned. "Well, definitely by morning."_ _

__Sherlock lifted his head and kissed him, pressed soft, swollen lips against his, and sucked lightly on his lower lip before sweeping his tongue across. John's darted out to meet it and they stayed that way for a long moment with open mouths and closed eyes. John felt a strange sensation of movement in his arse, and Sherlock laughed, breaking the kiss._ _

__"Sorry, slipping out. Just let me…"_ _

__John winced as he pulled out, and Sherlock got up to dispose of the condom. John sat up – carefully – and decided a trip to the bathroom might be a good idea. Five minutes later, they were back in bed, both of them yawning, with Sherlock's arm draped across John's chest._ _

__"Never would have pegged you for a cuddler."_ _

__Sherlock snorted. "M'not. This is all you."_ _

__"Then how come I'm enjoying it?"_ _

__"Because apparently your desire for post-coital cuddling is so strong that it overrides my body's aversion to it."_ _

__John chuckled at that. "Maybe we're rewiring each other's brains."_ _

__Sherlock made a groaning sound. "Oh, God, don't say that."_ _

__"It wouldn't be half-bad. You could set up a mind palace for me."_ _

__"That's not how it works." He yawned again and pressed a kiss against John's shoulder. "Are you normally this tired after sex?"_ _

__John closed his eyes and smiled. "Yes. Keeps me in the cave."_ _

__There was a moment of silence. "What?"_ _

__"Something Mary says. Never mind. Get some sleep. Round two can start in the morning."_ _

__Sherlock's breathing evened out within two minutes, and John drifted with the sound of it for a while before finally succumbing._ _

__*****_ _


	6. Six

The sound of running water woke him. John stretched and opened his eyes. He was alone, but the sheets were still warm next to him, and he smiled up at the ceiling. If all went well, he'd be back in his own body in a few hours, and the three of them could talk about how this arrangement was going to work. And before then, maybe Sherlock would like one more go, just the two of them.

Sitting up brought a bit of reality back to his morning-after bliss – fucking _ow_ , what the hell? He was going to have trouble walking for a bit, it seemed. He made his way to the bathroom, wincing, and stopped in the doorway.

"Morning."

Sherlock turned to look at him, toothbrush sticking out of his mouth. He nodded and turned back to the sink. John stepped around him to use the toilet, and then reached for the spare toothbrush he kept at the flat. 

"Funny how we didn't switch toothbrushes." 

Sherlock gave him a sidelong look and spat into the sink. "That'd be disgusting."

"Says the man who had his tongue up my arse last night."

Sherlock rinsed his mouth and smirked. "If you still want to use my toothbrush—"

"I'm not complaining, am I? You can do that anytime you like."

Sherlock leaned in to kiss his cheek. "I'm going to take a shower. Care to join me?"

John grinned through a mouthful of toothpaste.

The shower fantasy, it turned out, was more unrealistic than John had anticipated. They barely had room to turn around with both of them in the tiny tub at the same time, and John's attempt at a shower blow job nearly drowned him. There wasn't space to do much more than rub against each other, and when even that was complicated by their height difference, they finally decided it would be best to stick to cleaning themselves up and head back to bed.

Once there, John pressed Sherlock against the sheets and kissed him hard, and stroked both of their cocks together until he couldn't bear it any longer and rutted against him. It was far more erotic than he would have expected – so much warm, damp skin and just enough friction – and they gasped against each other's mouths, and oh, he was already too close.

"How do you want to come?" John asked, reluctantly putting a bit of space between them. 

"That was working fairly well." Sherlock pulled him back down again.

"Yes, but," John began, and then lost the train of thought for a moment, toes curling slightly when Sherlock arched up against him. He pressed his forehead against Sherlock's shoulder. "God, I want everything, all at once. I want to fuck you every way I can think of."

Sherlock's smile was nearly radiant. "If you like. It's your body, after all."

It was, wasn't it? John grinned and slid down to take Sherlock's (his own, fuck) erection into his mouth. It was a strange relief to know exactly what to do here: long, warm strokes, alternating between using his tongue and applying hard suction, then mouthing gently at his testicles, not too much pressure there, just enough to send delicious sparks of sensation up his spine. He pushed Sherlock's thighs back and moved lower, flicked his tongue across his anus, and Sherlock gasped and gripped the sheets under him. 

John wanted to fuck him, wanted it more badly than anything else, but it hardly seemed fair to make Sherlock deal with a body that hadn't been penetrated that way before. Instead, he slowly worked him open with his tongue, then pushed in a spit-slicked finger and took his cock in his mouth again. 

It was strange that he didn't know how this part felt: he'd never been fingered before, had pushed his partners' hands away when they'd tried. But Sherlock was showing no such reluctance, was writhing beneath him, hips pushing up into John's mouth and down against John's finger, strung between two points of pleasure. 

"Ah, fuck, right there," he said when John's fingertip pressed gently up, moving in as close to a circular motion as he could manage in that tight heat. 

He tried to coordinate the movement with his mouth, taking the shaft in as deeply as he could, using his tongue on the way up again, more and more suction. Sherlock's breathing was erratic now, punctuated with soft moans, and his hands clenched and unclenched at his sides. It was clear that this was something John should've tried before.

"Oh God, that's it, that's…" Sherlock thrust his hips up as he came, crying out, and John held on, stilling his fingers and his tongue and riding through it, just applying pressure, taking his cock in as far as he could. His mouth was flooded, and oh, that was weird – it had been a while. 

Sherlock pressed his hands over his face and groaned. "Fuck, that was amazing. God, your mouth."

[John sat up and swallowed – gravity was rather useful there, yes – and wiped at his lower lip with the tips of his fingers.](http://sherlock-addict.tumblr.com/post/79685480055/a-scene-from-an-amazing-fic-inexplicable) "Your mouth, actually."

Sherlock stared up at him, wide-eyed. "That is dead sexy, you know."

"That's a bit narcissistic, don't you think?"

"I don't care. That's what I look like after I've just sucked your cock for the first time." He paused, blinked, and looked away.

"Yes," John said, and crawled up his body and kissed him. "I know what you mean."

Sherlock pulled him close and threaded fingers into his own thick hair, turned John's head so that he could trace the shell of his ear with the tip of his tongue. "How do you want to come?"

"Mmmm. I'd like you to fuck me again, but—"

"Yeah, that's not happening for a few days." There was a smile against his neck. 

"Then touch me."

Sherlock kissed him again and rolled them both over, and warm fingers closed around his cock. Slow, teasing strokes, fingertips trailing over sensitive skin, tugging the foreskin back and forth. It was a long, steady build, and John sighed against Sherlock's lips.

"Could you keep doing that forever? Just like that."

"If you'll have me," Sherlock whispered, and just as John's eyes flew open, he slid down the bed and circled his tongue around one tight nipple.

"That too," John said, one hand already at the back of Sherlock's head. "Ah, fuck, make me come like that." 

And God, that tongue, and then teeth and lips and fingers, alternating between barely-there touches and intense sucks and bites that brought him to the knife's edge between pleasure and pain – all while one hand stroked his cock, slowly, deliberately. It was unlike anything he'd felt before. It nearly short-circuited his brain, and he finally couldn't think, could barely speak, just strained up against Sherlock and silently begged, on the edge of overstimulation.

"Please," he managed at last, fists tangled in the sheets and eyes squeezed tightly shut, "Oh God, please."

Sherlock seemed to vanish for a moment and John sucked in a breath at the sudden lack of sensation. He opened his mouth, intending to protest, and then Sherlock's lips closed around the head of his cock. John pushed his hips up, up into that glorious heat, and Sherlock made a soft sound of encouragement, and he did it again, and again, until he was fucking Sherlock's mouth outright. Sherlock held very still and kept his mouth slack, but after a minute he pushed John's hips back down to the mattress and sucked him in long, deep strokes, swallowing around him. 

John felt like he was falling in on himself, imploding, with his cock down Sherlock's throat and his eyes wide open. He was making a ridiculous amount of noise, but he couldn't control it. The orgasm roared over him, intense, sharp, fragile, and then finally faded away, leaving shockwaves behind. 

"Oh my God," he panted, once he could remember how to work his voice again. "Fuck, that was…fuck."

Sherlock was still sucking his cock gently, tongue carefully avoiding sensitive areas, and damn if it didn't still feel good. In his own body he'd be too sensitive, needing to withdraw, but now, here—it was amazing, almost soothing, like he was being taken care of, warm and wet and soft and loved. He closed his eyes and relaxed into the mattress, and let himself feel, soak it all in. 

Sherlock released him at last and pressed a kiss against his hip. "Sometimes I can get an erection again right away."

"Really?" John smiled, half a dozen scenarios flitting across his mind.

"But probably not when I've come four times in twenty-four hours."

John laughed, and then opened his eyes. "It's only been three. For me, anyway." John popped his head up to look at him. "Four for you?"

"Shower."

"Ah, right. But didn't Mary—"

"Yes, she caught me." Sherlock pressed his face against the mattress. 

John pressed one knee against his side. "And?"

"She… watched me finish."

"She didn't tell me that."

"Why would she? She thought I was you at the time. And we were all a bit distracted after."

"Why didn't you tell me?" John pushed up on his elbows, and Sherlock looked up at him.

"Are you angry?"

"No, just…"

Sherlock frowned. "You're jealous."

"No—"

"You are, you're jealous. After everything that's happened, how could you possibly—"

"No, stop." John sat up and sighed. "I'm a bit jealous, yeah, but not for the reason you think. She got to watch you get yourself off in the shower. I haven't done that." 

Sherlock stared at him for a full second, surprised. "That could be arranged, you know."

"I know, but… Wait, you were able to, with her watching?"

"I was really close when she came in, and hearing her voice..." He cradled his chin on his forearms. "I'm not usually attracted to women, so it was very odd. She just pushed back the curtain and stood there, and looked at me like... Like she wanted to climb in with me. And then she smiled and said, 'Go on, then.'"

"Sounds about right." 

"Is that something the two of you do often?" 

John grinned. "We have a running joke about catching each other wanking. I walked in on her in the bath once, Jesus. She had two—"

"No, no, I don't think I'm ready to hear this." Sherlock buried his face in his arms again, and sniffed. "On second thought, maybe I am. Two what?"

John laughed and took a deep breath, and then tilted his head. "Is that… coffee?"

Sherlock looked up. "Mary." 

They stared at each other for a moment. 

"We can't go out looking like this." 

Sherlock's brow furrowed. "She knows what we were doing. She probably heard you just now."

"I know, but… I don't know, it still feels weird. Get dressed." John forced himself to tamp down on his panic. She knew. She approved. It was fine. 

They got dressed quickly, and John felt his initial panic slowly morph into excitement. If she was here, it meant she knew how to switch them back. And then they could talk about the future, all three of them, with nothing in the way. 

"I'm looking forward to wearing my own clothes again," Sherlock said, wrinkling his nose at the shirt he was about to put on. 

"You aren't the only one," John grumbled, and fastened trousers that probably cost more than all of his own put together. And the man claimed not to care about the transport, honestly.

He turned to see Sherlock frowning at the bed, and oh, God – those sheets were fairly disgusting. He raised his eyebrows at Sherlock, who sighed and tried to tug the duvet over the lot. 

"I'd better go and see about—"

"Yeah, go." 

He opened the bedroom door and peered out cautiously, in case it turned out to be Mrs. Hudson again. Mary was sitting at the table with a cup of coffee and scanning the morning paper. 

He closed the door behind him. "Good morning."

She looked up at him briefly before turning back to the paper. "So I heard." 

"Did you?" 

"I think the neighbors probably heard, darling." There was a distinct smirk in her voice.

At least he'd sounded like Sherlock at the time. 

"I'll be right there, just a moment." He gestured awkwardly toward the bathroom door, and then opened it before he could make a bigger fool of himself. He washed up and stared at himself in the mirror for a long moment. Sherlock's face stared back at him – perhaps for the last time. These last two days had been strange beyond anything he could have imagined, but it was odd to think that it was almost over. 

He crossed to the kitchen and stopped to kiss Mary's forehead before pouring himself a cup of coffee. He sat across from her, somewhat gingerly, and took a deep breath. "So."

"So, it was a good night then?" 

"Yeah." Interesting that he wasn't blushing, though this would be horribly embarrassing in his own body. But of course, it was true, so what was there to be embarrassed about?

She looked up at him, eyes sparkling with humor. "Anything you can teach me how to do?"

"Some of it only works in his body, I think. But other things, yeah. Definitely." 

"Such as?"

John shifted forward in the chair and winced at the sudden discomfort that movement caused. "Well…"

Her eyes widened. "He got to try it before I did? You've no excuse now, John Watson. I'm doing a bit of shopping this afternoon, fair warning."

"I might help you. Fair warning." He stirred sugar into his coffee and grinned at her. 

"So… you liked it?"

"More than I expected. It was intense." 

"I've always thought men should experience being penetrated at least once." She raised her eyebrows and picked up her coffee cup. "It's intimate, isn't it? Letting someone else into your body like that. Giving over control."

"It is." He stared back at her, found he couldn't look away from her eyes.

She reached across the table to take his hand and traced her fingertips delicately across his palm. She wet her lips and stared down at their joined hands. "I'd like to see you like that. You, I mean. Not you in Sherlock's body." She looked up at him and made a funny face. "Don't get me wrong – Sherlock is adorable. I get why you like him, but… it's you I want."

He squeezed her hand. "How exactly is this going to work?"

"I've no idea." She looked thoughtful for a moment and took a breath before speaking again. "I'm going to have to get used to the idea of sharing you like that. I can't say I won't be jealous."

"I know. I'm sorry for what happened yesterday. I've no excuse."

"Well, you do have a bit of an excuse." She quirked an eyebrow at him. "It was the first thing I wanted to do when I switched with a bloke."

John gaped at her. "You… what?"

She bit her lip, clearly embarrassed now. "We wanted to know what it felt like in each other's bodies. Who wouldn't?"

"That… actually explains a lot." 

"Does it?" She smiled and took a sip of coffee. 

The bathroom door closed and they both turned to look. The sound of running water filled the flat, and Jesus, the walls really were thin, weren't they? 

John took a deep breath. "So… what are you going to be comfortable with, in this? Is it going to be me and you and then me and him, or would you like Sherlock to join us, or…?"

Mary opened her mouth, but hesitated for a moment before speaking. "I don't know. What do you want?"

"All of it." He'd said it more quickly than he'd intended, but there it was.

"Of course you do." She made a sound like a choked laugh. "What does Sherlock want?"

John's jaw clenched: he had no idea, truthfully. Sherlock wasn't generally attracted to women, but even now, John felt something for Mary – would some of that remain behind when they switched back? 

"We've got time to work it out. We don't have to rush into any of it." She smiled at him a bit cheekily. "If he wouldn't mind me watching, that might be a good place to start."

The bathroom door opened and Sherlock stopped at the edge of the kitchen, eyes sweeping over the scene at the table. "Everything all right?" 

"Yes," Mary said, and John was struck by her expression as she looked at him – at Sherlock wearing John's face. Sherlock stared back at her, and John could see the conflicting emotions there. "I was just about to ask John what you got up to last night."

"Ah, yes. Details and breakfast, in that order?"

"I brought breakfast, actually." She gestured to a bag on the kitchen counter behind her. "I reckoned you two probably wouldn't have got around to it."

"Oh, good. I'm starving." Sherlock brought the bag to the table and started rifling through it. "Oh, bacon and egg sandwich – I've never wanted one more in my life." He tore back the wrapper and attacked it.

"I take it you worked him hard last night?" Mary quipped, and reached for the bag.

"Apparently so." John smiled at her, exhilarated. It was weird, but it felt good, like it could work. It had to work – he wasn't sure he could bear to live without both of them. 

Mary handed him a sandwich. "So, I've got news."

Sherlock froze mid-chew and looked up at her expectantly.

"I met with an old friend overnight, and we found a solution. It's complicated, but it's still possible to switch you back with very little damage."

Sherlock made a sound of surprise through his mouthful of sandwich. He swallowed and glanced at John. "What sort of damage?"

"The longer you remain in this state, the more you tend to restructure the host brain. It can't be restructured completely, of course; it's more a matter of making modifications, just for survival."

"So the more modifications are made, the more damage is done?" There was a hint of panic in Sherlock's voice.

Mary's brow furrowed. "Perhaps damage is the wrong word. Change is more accurate. At any rate, there is a tipping point after which the amount of change is incredibly difficult to reverse, and the host's personality, memories, and thought processes are significantly altered." 

"Great," John muttered. He adored Sherlock, but he didn't want to be like him.

"In your cases, your relative isolation over the last two days has likely helped protect you from the worst of it. You didn't have the extra added layer of pretending to be each other constantly, and you knew each other well enough that it wasn't a complete shock. Our hope is that all of that allowed you to keep your brains fairly intact."

John glanced over at Sherlock, who'd gone rather pale. "Thibaud wasn't so fortunate, I imagine."

"So what do we do now?" Sherlock asked. "Can you take care of it?"

"I can't, not since… not anymore." 

"You..." Sherlock tilted his head and looked astonished. "You gave it up?" 

"Not exactly." Mary's smile was tight, and she looked away.

"Oh God." Sherlock stared at her, his expression surprisingly full of empathy. 

She blinked a few times. "It's not all bad. It was an adjustment, to be sure." She looked at John, her eyes bright. "And the new life I've found has made everything worth it."

John took a deep breath. There was still so much he didn't know, so much she hadn't told him. He had to trust that she would, in time. He reached for her hand. "I'm glad."

"Me too." She interlaced her fingers with his and smiled.

"Can we do this part later?" Sherlock asked, voice tinged with annoyance now. "If you can't do it, who can?"

As if on cue, they heard the distinct sound of the downstairs door opening, followed by footsteps on the stairs. Sherlock turned to Mary, his face suddenly stony. "Tell me you didn't. Not him." 

"I had to," she replied. "He already knew, anyway. What the hell were you doing, poking around that part of Charing Cross Road?"

"Trying to solve a case," Sherlock hissed in response. "I'd forgotten what was there until we arrived."

"You forgot?" She shot him a skeptical look.

"You know how the protections work."

John groaned and tried to tamp down his annoyance at being left out of the conversation yet again.

Sherlock pressed his hands over his face. "Fuck. _Fuck_."

The footsteps stopped just outside the doorway, and they all turned to look. After an interminable moment, the door opened, revealing a familiar figure.

"Good morning, all." Mycroft Holmes posed in the doorway, umbrella in hand. 

"Is it?" Sherlock replied with a sneer.

"I suppose it depends on one's perspective." Mycroft crossed to stand by the table, and his gaze settled on Sherlock in John's body. "Well, you've got yourself in quite a spot, haven't you, Sherlock?"

John swallowed down a bizarre urge to laugh. Of course none of this would seem remotely strange to Mycroft. _Of course._

"Come to rub it in, have you?" Sherlock's _fuck you, Mycroft_ expression looked bizarre on John's face.

"I've come to fix it, actually." He turned to John and paused, frowning. His gaze flicked back to Sherlock, and his eyebrows arched. "Well, that's an interesting development."

Sherlock rolled his eyes. "Get on with it, will you?" 

"First, you should know that I have informed the appropriate authorities in France about Monsieur Thibaud's predicament. This morning I received word that they'd found the culprit."

"Who?" John and Sherlock asked, simultaneously.

"Thibaud himself, as it turns out. His plan was to switch bodies with his romantic rival long enough to break off the affair with his wife, using a magical device he'd apparently acquired on a visit to London years before. He didn't realize it was malfunctioning until it was too late. I'm sure you can work out the rest."

"So the man everyone thought was Thibaud was actually Michel Tasse, the actor?" John shook his head.

"Yes. Thibaud decided to make the best of it, apparently. His antics created quite a media stir in Monte Carlo this weekend. But Monsieur Tasse had no idea what had happened and reacted accordingly. They'll be switched back, for better or worse, and Thibaud will be dealt with by the appropriate government agency." Mycroft's steely gaze settled on Sherlock. 

"Once again, I didn't know what it did." Sherlock's tone bordered on whinging, and John had the distinct impression he and Mycroft had had very similar conversations before. 

Mycroft crossed to the sofa table and looked down at the large pile of matchboxes covering it. He picked one up and turned it over in his fingers. "Relax, little brother. Being what you are – or rather, what you are not – you won't face any consequences."

Sherlock's jaw clenched and he looked away, and John frowned. "What do you mean, what he's _not_?"

"Just that the authorities will consider the case an accident." Mycroft turned back to face them and pocketed the matchbox. "There was clearly no malicious intent. Though this is hardly the first time Sherlock has overstepped his bounds and dabbled in things he's unqualified to deal with." Sherlock held up two fingers in response and Mycroft rolled his eyes. "I remain hopeful that one day, he will learn his lesson." 

John's gaze drifted past him to the table again, and to his astonishment, it was now bare. The pile of matchboxes had vanished into thin air. "What the—"

"Mycroft, don't antagonize him," Mary said, and John turned to look at her. "It wasn't Sherlock's fault. As far as he knew, it was just a case."

"And I do thank you for bringing it to my attention, Alice." Mycroft's expression softened slightly. "At great personal risk to yourself."

John frowned, certain he'd misheard. "Alice?"

Mary's cheeks tinged. "I went by Alice at school. Never liked it much." 

"Ah yes, it's Mary now, isn't it? So sorry." Mycroft's face was a mask of pleasantry. 

John gaped at her. "You went to school with Mycroft?"

Mary looked distinctly uncomfortable. "He was several years ahead of me. We hardly knew each other."

John turned to Sherlock. "So does that mean that you knew Mary at school as well? Has everyone been lying to me for months now?"

"No, I went to public school." Sherlock shot Mycroft a murderous look. "I was never quite as _special_ as Mycroft, you know."

"It always did worry Mother." Mycroft's voice dripped with more sarcasm than usual. "Now, I've many important things to do this morning, so if you wouldn't mind getting on with it."

"Yes, let's," John said, standing. "The sooner we do this, the sooner we can get back to more important things. Where do you want us?"

"You should probably sit somewhere comfortable, in case the experience of returning to your own body proves to be disorienting."

"Right." John gestured across the room to their chairs, and Sherlock followed, still sulking. They sat in each other's chairs and Mycroft crossed to stand before them. Mary stood just behind him, looking as anxious as John had ever seen her.

Sherlock exhaled, slowly, and suddenly seemed nervous. John watched him for a moment before turning to look at Mary and Mycroft, and a spike of anxiety shot through him. All three of them knew more about what was happening than he did. And all three of them looked nearly terrified. 

"Remain still," Mycroft said, his voice unusually soft. "This is a rather delicate procedure." He frowned in concentration. 

John fought the urge to close his eyes against the fear that welled inside him. He looked at Sherlock instead, at his own face. How strange that it would soon be his again, that everything he'd grown used to in the last two days would vanish. And there were things he hadn't done, hadn't tried – would he look back and regret that? Sherlock turned to look at him then, and John's heart pounded in his chest.

Even if it cost them something, even if they were never quite the same, it had been worth it. 

From the corner of his eye he saw Mycroft hold his umbrella before him like a lance, and he spoke words John didn't understand. 

Everything began to go dark around the edges, slowly narrowing down to a small circle of light, down to just his own face with wide, startled eyes. There was a strange pressure in John's chest and he gasped for breath. He could feel his consciousness fading, could hear voices raised nearby, but even those began to recede. He tried to focus, but it was like grasping at the tendrils of a dream. 

And then there was nothing.

*****

"John? John, are you all right?"

He was sitting in a chair. He stretched out his fingers and felt worn, familiar leather: it was his chair at the flat on Baker Street, actually, and bloody hell, his head was splitting. He winced and pressed a hand to his temple.

"Ah, shit. What happened?"

"You passed out, you and Sherlock both. God, you had us worried." Mary's voice shook slightly and she touched his cheek. Her fingers were cool.

"Passed out? What the hell happened? Sherlock?" He opened his eyes and blinked. The world was weirdly blurry.

"He's coming around," someone said, and John looked across the room. After a moment, his eyes focused: Mycroft was standing by Sherlock's chair, leaning over him, his face showing more brotherly concern than John would have thought him capable of.

There was a groan and then Sherlock said, "What are you doing? Stop it."

"I need to see your eyes," Mycroft said, his voice taking on the sort of patient tone John used when working with small children. "Come now, focus on me. What's the last thing you remember?"

Sherlock squinted up at him, and then frowned. "I was… I… don't know." He looked over at John, clearly bewildered.

A feeling of panic settled in the pit of John's stomach. "I was working on the blog, maybe." He tried to focus his thoughts. "Or no, wait – I was going to do. That's why I came over this morning."

"Yes, and I was going over cases." Sherlock looked up at Mycroft, his expression oddly vulnerable. "What are you doing here?"

John blinked in confusion: yes, what were they doing there? "Oh God, I haven't even introduced you properly, have I? Mary, that's Sherlock's brother Mycroft. Mycroft, this is my fiancée, Mary Morstan." John looked up at Mary, who had gone pale. "What is it?"

"You don't remember anything? This morning or yesterday, or…" She took a step back, one hand over her mouth.

"Yesterday?" Sherlock's voice had a hint of panic now as well. "What day is it?"

"Monday," Mycroft said. "Oh, dear."

"Monday?!" John turned to look at Sherlock again. "What the hell happened?"

"You didn't say anything about memory loss!" Mary spat, and it was a moment before John worked out who she was talking to. "You could have mentioned that before we—"

"It was only two days," Mycroft replied, waving his hands dismissively. "What could possibly have happened in that amount of time that would be so important to remember?"

Mary shook her head, as angry as John had ever seen her. "You did this on purpose!"

"I did no such thing."

"Bill offered to do it, but you had to poke your nose in, didn't you? You couldn't resist the opportunity to take a petty shot at your brother."

Mycroft rolled his eyes. "Must we be so very dramatic? There was always a risk of memory loss. You should have expected that much. They're both lucky they didn't suffer permanent damage."

"They've lost the last two days! How is that not damage?"

"The memory loss may be temporary. There's no way of knowing at the moment."

John's head throbbed, and he groaned. "Will someone explain what the hell is going on?"

Mary closed her eyes and shook her head, put a hand over her mouth. She almost looked as if she might be sick. 

"Yes, Mycroft," Sherlock said, an unfamiliar edge to his voice. "What exactly happened to us?"

Mycroft turned to John. "You've both been behaving erratically since Saturday morning. I suspect it may have been the result of one of my brother's experiments." 

"Experiment?" Sherlock repeated, his voice strained. "Don't be ridiculous. I wouldn't experiment on both of us at once. What would be the point?"

John gaped at him. "You've been experimenting on me?"

"Not recently." Sherlock didn't quite meet John's gaze.

Mycroft sighed, pointedly. "At any rate, Mary alerted me to the problem last night, and we arrived early this morning to find you both nearly delusional. We administered a sedative to you both and contacted a discreet pharmacist for a solution. Consider yourselves very lucky."

"Oh my God." John pressed his hands against the sides of his aching head. "Did it not occur to you to take us to A&E?"

"And risk another embarrassing scandal?" Mycroft snorted. "No, this was for the best. You'll both be perfectly fine in a few hours, though there may be some lingering dis-ease."

"And Jesus, it's Monday – I've got to get to the clinic."

"You'll do no such thing," Mary said, and he turned to look at her. "I've called in sick for you." Her face was still pale, and she looked stricken. She'd been worried, clearly. Jesus, he couldn't imagine what it must've been like, to see him like… whatever it was. _Delusional_. He probably didn't want to know. God, an entire weekend? 

He reached out for her hand and pulled her closer. "It's all right. I'm all right."

"I know. I know you are, you both are. I just…" She pressed her lips together and closed her eyes, and looked as if she was trying very hard not to cry. 

John stood, apparently too quickly; he swayed from vertigo for a moment before reaching out for the back of the chair, and still missed it by a good four inches. He finally managed to pull her into his arms, and she buried her face in his shoulder. He was almost overwhelmed by the urge to hold her, to kiss her. It was as if he hadn't seen her for weeks.

He turned his head to glare at Sherlock. "What did you do?"

Sherlock looked up at the ceiling. "Why are you taking Mycroft's side?"

"I'm taking my own fucking side. Jesus, Sherlock."

Sherlock slid forward in his chair and then froze, a strange expression on his face. He blinked and looked up at Mycroft, who smirked at him.

"Well, I must be going. I've wasted enough time sorting you two out this morning." Mycroft tucked his umbrella under his arm and headed for the door.

"Mycroft," Mary said softly. She pulled out of John's embrace, and Mycroft turned back to look at her. She stiffened her spine and held her head high. "Thank you for your… assistance."

"Of course. I do wish you all the best in your new life." He pressed his lips together in an approximation of a smile and left without another word.

Sherlock made a hissing sound, almost as if in pain, and John turned to look at him. He was standing uncomfortably next to his chair and staring around the flat as if he hadn't seen it in a long time. 

Sympathy overcame John's anger, as always. "Are you all right?"

Sherlock frowned and stared down at the sofa table. "Mary, do you have any idea what happened?"

Mary was silent, her expression nearly unreadable, as if she was unwilling to let them see how much this – whatever this was – had affected her. "I wasn't here when it happened. John actually hasn't been home since. He's stayed here with you the entire time. We thought it was better that way."

John turned to look at Sherlock, who'd gone even paler than usual. "Sherlock, are you sure you're all right?"

Sherlock's eyes finally met his, and John felt a strange wave of emotion. Something wasn't right here, but he couldn't put his finger on it. Sherlock stared back at him with a look of utter confusion for a full second, and then looked away again. "Everything looks odd, doesn't it?"

"It does." 

"I'm just going to… excuse me a moment." Sherlock headed across the flat in the direction of the bathroom, walking a bit stiffly. 

John frowned after him. Whatever had happened, Sherlock didn't seem to remember doing it. John could hardly stay cross with him when it had affected him just as drastically. Perhaps it would make him think twice about doing something like this again. One could hope, at least. 

"I'm glad you're both sorted," Mary said after a moment, though she sounded anything but. She turned to John and smoothed down the front of his shirt, her gaze fixed on his chest. She looked deeply sad in a way he'd never seen before.

John felt a twinge in his chest. "Look, Mary – I have no idea what happened these last two days, but if I did something—"

"No, it isn't like that," she said, and looked up at him. She looked as if she wanted to say something more for a moment, and then looked away again. "I've got to go in to the clinic this morning, but you should stay here, get some rest. I'll swing by this evening and take you home."

"All right." The world wobbled a bit, and John settled in the chair again and exhaled. He felt weird, like his skin was crawling. Everything felt wrong, somehow. 

"Mycroft said the memory loss might be temporary. Maybe it will come back to you, if you give it time." 

John sighed and nodded, but he wasn't convinced. 

"You should spend more time with Sherlock. Find a case, maybe."

John snorted. "Because that worked out so well this weekend."

"I mean it. I know how much you miss each other."

"Sherlock misses having an audience, mostly."

Mary looked away, her expression suddenly strained. "I've a wedding to plan, anyway. You could keep each other entertained."

"He could have it all planned for you in a single weekend, if you let him."

"There's an idea. I should ask him to help." She looked back at him again, but her smile didn't completely reach her eyes. She leaned over and kissed him, then pressed her lips against his ear. "Don't be too hard on him. He loves you, more than you know." She stepped back then and gave him a small smile, and crossed to where her coat hung by the door. 

John watched her leave, bewildered. What the hell had she meant by that? 

There was a sound behind him and John turned to look. Sherlock emerged from the bedroom and pulled the door firmly shut before closing his eyes and leaning back against it. His expression was unusually tense, enough that John was momentarily taken aback. Sherlock could usually work out everything from a mere handful of clues. This situation, with its mysterious cause and days of memory loss, must be driving him half-mad. 

Unless, of course, he had worked it out.

John stood again and swayed a bit before trusting his legs to take him to the kitchen. "Sherlock, do you have any idea how this happened?" Sherlock didn't reply, just stared straight ahead, and John sighed. "Look, if it was something you did, even if it's something you think would piss me off, just tell me. Please."

"I don't…" Sherlock began, and then shook his head. "I don't know how it happened." He looked shaken, and John felt a strange impulse to walk over and hug him. 

Christ – perhaps he'd suffered a head injury after all. John rubbed at his temples and sighed. "I want some coffee."

"I've already had some. I think." Sherlock frowned. 

There was indeed a pot of coffee on the counter, and several half-drunk mugs on the table. He frowned and picked one up, and took it to the sink to rinse it. He poured another cup and reached for the sugar bowl, and froze. 

It was as if he'd reached for it out of habit, which made no sense whatsoever. He shook his head and crossed back to his chair. He needed to do something else, get his mind off it for a bit. There was a stack of newspapers sitting on the sofa table and he picked one up.

Sherlock stood by the fireplace now, looking unbearably young and lost. John watched him for a moment, feeling an odd surge of affection. He did miss Sherlock. It was the reason he'd come over this morning – or the other morning, rather. Just being around Sherlock was weirdly soothing. He loved Mary, of course, but Sherlock… 

God, he hadn't thought about that in a while. He looked away, swallowed, exhaled. Best to let that particular dragon sleep. He'd moved on, and it was for the best.

Sherlock was still for a moment, and then crossed toward him with slow, hesitant footsteps. John looked up to see him staring down at something in his hands – a pair of reading glasses.

"Whose are those?" 

Sherlock's mouth opened, and then closed again, and he shrugged. "They're yours. Aren't they?" He handed them to John.

"I don't use reading glasses," John said, but took them all the same. They did seem familiar, oddly. He couldn't remember seeing them before. Had he actually bought reading glasses in the last two days? He put them on and grinned up at Sherlock. "I probably look like my father in these."

A smile played at the edges of Sherlock's mouth. "It suits you."

"Are you implying that I'm getting old?" He snorted and looked down at the newspaper in front of him, and then blinked in surprise at the sudden clarity of the print on the page. "Damn. That actually helps. I must need a vision check." He looked up again, frowning.

Sherlock stared back at him, a strange expression on his face.

"What?" 

Sherlock shook his head slowly, his eyes searching John's face. "I don't know."

"That's not something I hear very often."

Sherlock opened his mouth, as if he wanted to say something more, but he didn't. He crossed back to his chair and sat, rather uncomfortably. He clenched his jaw and frowned, and reached into his pocket.

"Sherlock, are you…?" Sherlock looked up at him and John's breath caught. He swallowed, his nerve lost. "Hungry?"

Sherlock's lips twisted into something almost like a smile. "No." 

"Right." John returned to the paper again. Best not to dwell on it too much. He'd drive himself mad wondering what might've happened over the last couple of days. 

They were both quiet for a while. John finally couldn't bear it any longer and risked a glance at Sherlock. He was sitting very still and staring at a small object held between his fingers. 

"What is that?"

Sherlock looked up. "A French decathlete found completely out of his mind, surrounded by one thousand, eight hundred and twelve matchboxes – all empty except this one." 

"And what's in that one?"

Sherlock slid the matchbox open and peeked inside, shook it, and shrugged. "Nothing."

~ _fin_ ~

**Notes for the Chapter:**

> Thank you for reading, and special thanks to everyone who has followed this story as a WIP and commented along the way. I appreciate it more than you know! 
> 
> And before anyone sends me hate mail, I do have a sequel in mind for this story, though I probably won't get to it for a while.
> 
> [Gifset](http://sherlock-addict.tumblr.com/post/79685480055/a-scene-from-an-amazing-fic-inexplicable) by sherlock-addict.

**Works inspired by this one:**

  * [Inexplicable Cover Art](https://archiveofourown.org/works/1274734) by [consultingpiskies](https://archiveofourown.org/users/consultingpiskies/pseuds/consultingpiskies)




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